CONOSCENZA

**KNOWLEDGE** — From the Latin *cognoscere* (cum-noscere, Gr. γιγνώσκειν and γινώσκειν) it is the act by which a being (subject) becomes aware or perceives something (object). It is the characteristic activity of the higher degrees of life, which qualifies and distinguishes them through the gradual perfection of its forms.

**OUTLINE:**

I. Knowledge in general

II. Theory of knowledge.

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### I. KNOWLEDGE IN GENERAL

#### 1. Concept
The term *knowledge* presents various meanings, even though they are complementary and related. It can indeed designate: 1) the act itself of knowing or learning; 2) the content or object of knowing: a meaning that is less frequent and less technical. Although Italian has two general terms, *knowledge* (*c.*) and *cognition*, it does not draw a clear distinction between them in meaning, even though *cognition* is more commonly used to express the content of knowing than *knowledge*. The term *conoscimento* (connaissance), though increasingly rare, is technically more precise for indicating the act of knowing. Primarily in relation to content, the term *knowledge* is mostly taken in a very broad sense and then designates: 3) any apprehension of an object, regardless of its degree, form, or certainty; but it is sometimes restricted to indicate 4) a clear, distinct, and relatively perfect apprehension, approaching the meaning of *sapere* (to know, as in "to have knowledge of a doctrine, of a science"). However, to indicate the distinct and essential knowledge of an object, the term *comprendere* (to understand) is more precise, distinguished from *conoscere* (to know) as a species of the genus (cf. Gr. γιγνώσκειν, εἰδέναι and Ger. *kennen*, *wissen*). Similarly, although *knowledge* is sometimes used, especially in modern philosophical language, as a synonym of *consciousness* (v.), more precisely *consciousness* is a particular form of knowledge, namely, the knowledge that the subject has of its own psychic states and contents as such, and of itself as subject. Although, in a very general sense, *consciousness* can also indicate the fundamental and characteristic modality inherent in knowledge, by which its contents are "given" and made "present" to the knowing subject. While thus *consciousness* in a general sense emphasizes rather the objective presence implied in the fact of knowing, it is inherent in the original meaning of *knowledge* the objective relation and direction, inasmuch as it immediately indicates the subject's reference to an object as the term of apprehension or perception.

Knowledge, as an original fact arising from the mysterious depths of being and life, cannot, properly speaking, be expressed in more immediate concepts; even though it is possible to clarify the cognitive act through an analytic and dialectical examination of its process, its conditions, its postulates, limits, and value (v. below: Theory of knowledge). Knowledge is in fact an original experience whose character is immediate, primary, and absolute; indeed, in its broadest sense, it is experience itself, the ground in which every representation, notion, and conscious fact is situated. The explanation of knowledge through metaphysical concepts and sensible analogies undoubtedly helps to highlight implicit aspects and values, but it would not illuminate the specific reality of knowledge unless one returns to the immediate experience of knowing itself, by which those same concepts and analogies are actualized and given as contents of consciousness. Therefore, the qualification of knowledge as "image" and "representation," while it helps to indicate the objective character inherent in the concept of knowing, does not in reality clarify what knowledge is unless the image is understood as the conscious presentation of an object (intentionality). Moreover, "image" and "representation" can here take on an ambiguous meaning if one were to attribute to them a physical consistency, severing them from the cognitive act. Knowledge is "representation" insofar as it is itself "presence" (note the etymological proximity of the two terms). But "consciousness," "presence," "intentionality" are terms that do not acquire for us a precise and defined content unless they are referred to the original experience of knowing.

Knowledge, therefore, as an immediate intuition for common experience (nothing is clearer or more intuitive than expressions like: "I see a tree," "I know a problem," "I know a science"), in its radical metaphysical structure is for human thought a reality no less obscure and profound than the objects that are given to it in consciousness; and it is extremely difficult to clarify the first ontic condition that lies at the root of its being-in-the-world. Its reasons are lost in the very mystery of the Absolute, of which knowledge is certainly a necessary form, but which, having neither causes nor principles, is, in its original determination and essence, incomprehensible to human thought. How it is possible, on what first determinations and properties of being this fact arises—that some things not only exist but know that they exist and perceive the existence of other things—is as inexplicable as, fundamentally, existence itself is inexplicable. The bio-physiological conditions of cognitive processes, which science, within the limits of its possibilities and aims, succeeds fairly well in clarifying, and which materialism considers the ultimate explanation of knowledge, in reality leave the problem of the nature of consciousness intact. Consequently, when it is said that the act of knowing is clear and transparent to itself, this can only be understood within the limits of the conscious presence of the data or contents and, possibly, of the act of knowing itself when it becomes an object in reflexive knowledge; not at all on the plane of the nature and being of knowledge. The act of knowing, as it is given in immediate explicitness to the subject who expresses it (to a large extent unbeknownst to him, as in the entire sphere of lower sensitive life), remains in its conditions and causes, like every other natural and vital process, unknown to itself, until reflection, taking it as an object, clarifies it on the plane of science and philosophy.

Within the limits of the above observations, however, the formulas by which, particularly Aristotle and St. Thomas, attempted to translate into conceptual terms the universal fact of knowing, undoubtedly have explanatory value. One must hold universally, Aristotle affirms, that sensation consists in receiving the forms or sensible images without matter (ἡ μὲν αἰσθησις ἐστὶ τὸ δεικτικὸν τῶν αἰσθητῶν εἶδος ἄν τις ὄλης).

De an., II, 12, 42 a 17 et seq.), just as wax receives the impress of a seal without becoming either iron or gold. St. Thomas, commenting on this passage, notes that, in the final analysis, the reception of formal determinations is proper to every patient when it undergoes an effect from an agent (e.g., air when heated by fire). But in the case of knowledge, what is essentially different is the manner in which the form is received. While in every other physical relation of cause and effect, action and passion, the form repeats in the patient the same mode of being, of natural-entitative existence, that it had in the agent, in knowledge, however, the mode of being of the form in the subject as knowing is different from its mode of being in the object; namely, not entitative-real, but representative-intentional. This is due to the fact that the receptive disposition present in the knowing subject as such is not a passive potentiality for actualization in the order of being, but rather an active principle of assimilation—in degrees of possessive consciousness more or less profound—of forms: “Et per hunc modum sensus recipit formas sine materia, quia alterius modi esse habet forma in sensu et in re sensibili. Nam in re sensibili habet esse naturale, in sensu autem habet esse intentionale et spirituale” (In De an., II, lect. 24, ed. Pirotta, n. 553).

The ultimate and sole root of this potentiality, according to St. Thomas, is founded in the immateriality and spirituality of the knowing subject, by which it is not entirely confined within the limits of its natural being: “... cognoscentes et non cognoscentes in hoc distinguuntur quia non cognoscentes nihil habent nisi formam suam tantum; sed cognoscens natum est habere formam etiam rei alterius. Nam species cogniti est in cognoscente. Unde manifestum est quod natura rei non cognoscentis est limitata. Natura autem rerum cognoscentium habet maiorem amplitudinem et extensionem... Creatio autem formae est per materiam. Patet igitur quod immaterialitas alicuius rei est ratio quod sit cognoscitiva; et secundum modum immaterialitatis est modus cognitionis” (Sum. Theol., I, q. 14, a. 1, c.).

This principle is connected with the general presuppositions of the hylemorphic system, according to which matter, as such, cannot receive form except as a metaphysical principle actualizing its essential ontological indeterminacy and thus as a real principle.

Consequently, what is given in knowledge—whatever order of entity it may belong to—assumes in the subject a presence that is immaterial, the value and intensity of which is proportional to the degree of the subject’s ontological spirituality. This immaterial presence, from the standpoint of metaphysical belonging, is a mode of being of the subject itself: for, in the final analysis, it is nothing other than the subject’s becoming spiritual, the determination of its representative potentiality in the order of consciousness. The scholastic dictum “cognoscens in actu est cognitum in actu” (cf. Sum. Theol., I, q. 85, a. 2 ad 1) precisely intended to highlight the extreme unity realized in the act of knowledge between the knowing subject, as an objective-conscious actuality, and the content of knowledge itself.

In relation to the notion of knowledge as the formal becoming of the subject, Aristotle already observed that the knowing subject, not limited to its natural mode of being, can in a certain way, through sensitive and intellectual knowledge, become all things: “ἡ ψυχή τὰ ὄντα πῶς ἔστι πάντα” (De an., III, 8, 432 a 29), and St. Thomas saw in this property of knowledge a certain likeness of the soul to God Himself, the metaphysical and conscious synthesis of all reality: “Et sic anima hominis fit omnia quodammodo secundum sensum et intellectum, in quo cognoscentia ad Dei similitudinem quodammodo appropinquant in quo omnia praeexistunt” (Sum. Theol., I, q. 80, a. 1, c.; cf. In De an., III, lect. 13, nn. 787–90). Knowledge is thus represented almost as a surpassing of the necessary limitation and ontological determination of beings to their own degree of reality, expanding them, in the intentional order, into the reality and perfection of the universe (De ver., q. 2, a. 2; q. 23, a. 1).

The notion of knowledge implies in itself the dualism of subject and object, of the principle of consciousness and its content. Even in the possible fundamental identity between subject and object, as in the case of thought thinking itself and its acts (the reflexive power belonging exclusively to spiritual knowledge), the gnoseological duality between the two terms persists: the thinking thought (I, mind, spirit) always retreats as subjectivity to the roots of the act and does not establish the cognitive relation except insofar as it distinguishes itself from itself, making itself the object of its own gaze and contemplation—a psychological-gnoseological reality clearly expressed in language that contrasts objects and subjective contents of knowledge with knowledge itself: “my seeing, feeling, thinking.”

The original concept of knowledge therefore does not, in itself, suggest the idea of the subject’s positing or creating the object, but rather of a representative conformity of the subject to the object, whatever the entitative structure and relationship between them may be. Thus, immediately connected with the fact and the idea of knowledge is the concept of “alterity” in gnoseology between subject and object. This indicates the relative opposition of the two terms and must not, as is evident, be confused with spatial separation or distinction. The latter is entirely indifferent to the cognitive relation, which is not thinkable in spatial terms but solely in terms of consciousness: it is a relation between the principle and term of an immanent action, between consciousness as an active potentiality for actualization and the “content” in which it actualizes and determines itself. In this immanent relation, spatial distance itself is resolved and surpassed when, in both sensitive and intellectual knowledge, something becomes the object of knowledge.

The dualism and alterity of subject and object necessarily lead to the concept of knowledge as “relation.” For even if, in the purely entitative order, knowledge, as a mode of being and determination of the subject, can and must be referred to the category of quality, nevertheless, by virtue of its intrinsic reference to “the other that is immanent to it,” it, while positing itself as a quality of the subject, is simultaneously determined as a relation. It must be noted at once, however, that since knowledge is accomplished through an immanent process in the subject, the relation it implies is not mutual but unilateral: it involves a positive becoming and actualization in the subject, which through it intentionally expands into the sphere of objects, but does not imply anything real in the thing known, which, by the mere fact of becoming an object of knowledge, gains nothing and loses nothing—being known is, in the final analysis, not a new reality for the object. This does not, however—and this is quite another matter—prevent the object’s becoming an object of knowledge from sometimes entailing positive consequences for the object itself when it falls within the sphere of the subject’s practical activity.

The concept of knowledge as relation immediately opens the analysis to other important conceptual determinations. As a relation between subject and object, knowledge implies the union of both in conscious representation; as a unilateral relation, it implies activity on the part of the subject; as such, it raises the problem of the relation of knowledge. Without delving deeply into the dialectical perspectives opened by these categories, it is easy to see how the most serious gnoseological problems—and indeed, in substance, the problem of knowledge itself—are articulated within them.

The *tivo*, while implying two terms, is a living unity of object and subject; indeed, in the final analysis, the subject itself has intentionally become the object. The fact of consciousness (*c.*) seems to point toward a radical identity of being and consciousness, or at least toward their essential metaphysical implication, which would serve as the very reason for the possibility of consciousness in general. Yet it must be noted that this is a universal metaphysical exigency that exists in the absolute order of being and leaves intact the real dualism of human consciousness. Indeed, whether in experience or in the intellectual consciousness of the world and reality, the essential gnoseological unity of all knowing does not resolve, on the plane of human consciousness and being, into metaphysical unity. This is what idealism (see below) has sought to deny, attempting an explanation of consciousness solely in absolute terms but thereby coming into conflict with the most evident exigencies of experience and transferring into the plane of human immanence those very reasons and postulates that are transcendent to consciousness in general.

Consciousness as activity raises the problem of the structure of the knowing subject and, consequently, of the conditions presupposed within it for the very fact of consciousness—conditions that thus emerge as determining factors of its value. Indeed, even if experience and reflection clearly show that human consciousness, particularly in its lower degrees where the ontic duality of subject and object is most pronounced, does not occur except through a certain influence and determination emanating from the object (an influence and action that largely unfold below the sphere of consciousness and in sensation as a purely natural, physiological-psychic process), it remains evident that intentional assimilation is an operative process that actualizes the ontological potentialities of the knowing subject. These potentialities naturally vary according to the degree and value of being in which the subject is situated. Hence the character of relativity and limitation that qualifies conscious assimilation from within, a relativity implicit in the scholastic principle that one knows according to the mode of the knower (*cognoscens secundum modum cognoscentis*) (Sum. Theol., 1a, q. 12, a. 4, c.), a specific application of a more general experiential principle: "receptum est in recipiente per modum recipientis" (ibid., q. 84, a. 1, c.). Yet here too it is of paramount importance to note that the conditioning function inherent in conscious assimilation, as St. Thomas himself clarified, can pertain solely to the mode of being of the thing known and does not in any way imply a deformation or transformation of its ontological content (cf. Sum. Theol., 1a, q. 14, a. 6, ad 1).

Certainly, the scholastic principle cited above implies that consciousness is proportionate to the cognitive powers of the subject: more or less extensive and adequate to the object according to the limits of those cognitive powers and their possible historical development into higher and more mature forms. Senses specifically different from ours, or more refined, may grasp new aspects of the sensible world; deeper intelligences may reveal more hidden problems and values in being; yet this does not mean that within the limits of our human knowing we do not grasp, albeit partially and through laborious logical-abstractive procedures, true and positive aspects of reality and being. Thus, one cannot conclude from the relativity of the cognitive act that consciousness is deforming or merely subjective—especially where consciousness (intellectual) reveals itself as expressive of universal and necessary values and thereby opens, within human consciousness, a perspective on the Absolute. To condition is not necessarily to transform. Every conditioning function is surpassed when what is given in consciousness—for example, even the simple self-consciousness of thinking beings—asserts its character of absolute and therefore unconditioned *ought-to-be*. In this case, it is not the subject that conditions the object but rather the object that conditions the substance and mode of the cognitive act; or rather, the object reveals its radical unity with the subject, being with thought. The becoming of reality as an object of consciousness in human thought is not then a conditioning or alienation of reality from its positivity, but rather a clarification and, as it were, a becoming-conscious of reality itself. And it is precisely because of its unconditioned value, emerging particularly in the evidence and conscious certainty of its subsumed moment, that intellectual consciousness raises the problem of the absolute and therefore objective structure of human thought and of its metaphysical dialectic toward the transcendent.

2. **Division.** — In relation to the diversity of its object, the fundamental division of human consciousness is into sensitive and intellectual. The former concerns the material properties and qualities of corporeal objects (extension, weight, solidity, colors, sounds, etc.) and the physiological-psychic modifications of the knowing subject itself (the vast complex of organic sensations, of which pleasure and pain are fundamental species); the latter refers to values and contents that either abstract from sensible properties (e.g., the value of being, substance, cause) or even deny them (e.g., the concepts of truth, spirituality, God). Intellectual consciousness, in particular, involves a plexus of important problems concerning the formal structure of thought (logic), the subjective conditions and causes of its being and becoming (psychology), and the determination of its value in relation to the objective apprehension of reality in its being, its causes, and its principles (theory of knowledge).

Analogous, though not identical, is the division of consciousness into empirical and rational: the former concrete in the facts of experience (thus including spiritual experience); the latter in values (concepts, judgments, and principles) that lie beyond experience, on the objective plane of intelligibility and rationality, even if they are founded upon and derived from experience itself. In relation to both its object and its own psychic modalities and conditions, consciousness is concrete (or intuitive) when it apprehends individual reality in the characters, modes, and forms of its real existence; it is abstract (or abstractive) when it apprehends the universal. It is immediate if it concerns objects that, in their empirical reality or rational evidence, are present to the subject *per se*; it is mediate or derived if it concerns contents or values whose character of evidence and certainty consists only in their connection to original objects and data (immediate experiences and principles). In relation to the different planes on which, in the scale of beings and values, its contents are distributed, consciousness admits three principal distinctions: spontaneous, scientific, and philosophical. With regard to the function that tendencies and affective conditions of the subject have in the origin and qualification of the object, consciousness is contrasted with purely rational consciousness as affective, sentimental, or mystical consciousness. According to the diversity of logical procedures, consciousness is inductive if it proceeds from data and facts of experience to rational values and principles, deductive if it unfolds rational principles into their consequences and formal derivations. Particularly after Kant, the division of consciousness into *a priori* (see) if it precedes experience, and *a posteriori* if it derives from experience, has become common. Intuitive, though not without problems, is the distinction of consciousness into actual and habitual.

II. Theory of knowledge — Knowledge in general and the forms it assumes in human experience present, as has already been indicated, a complex of philosophical problems of supreme value. Theory of knowledge is precisely the systematic treatment of such problems. It may be defined as: philosophical inquiry into the meaning and metaphysical value of knowledge in general and of the particular forms of human knowledge. The term, which seems the most suitable and comprehensive, is in general use in Italian (replaced by the equivalent Greek «gnoseologia») and in the Germanic languages (Erkenntnistheorie), and is now also more frequent in French, while English prefers epistemology (etymologically = doctrine of science; V. Epistemology). The term «criteriology», used by Balmes and later popularized by Mercier, is today largely abandoned, while the term, deriving from Kant, «critique» (of knowledge) is frequent. Other recently proposed terms («noology», «noetics», «ideology») have a restricted etymological meaning and have not succeeded in imposing themselves.

1. Systems

An adequate survey of the solutions to the problem of knowledge would in substance amount to a history of philosophical thought, given the central position which the problem of knowledge, by its very nature, assumes not only in modern philosophy but also in medieval and Greek thought. For indeed, nothing has value for man except insofar as and how it is in his knowledge; the problem of knowledge and its value implies and resolves within itself the problem of every other value, the problem of art, of science, of morals, of religion, of metaphysics, and, in the end, the problem of being. It is therefore not accurate what has often been repeated, that the problem and particularly the «theory» of knowledge is proper to modern philosophy. Modern philosophy has certainly felt in a more mature form one particular aspect of the problem of knowledge, namely the question of the «critical» method and process for a valid solution, and has attempted, which is not found in the ancients, a development of epistemology distinct from metaphysics; but there is no doubt that questions and concerns about the value of knowledge already appear at the dawn of Greek philosophy: even if one can and must admit, in broad outline, the fact that human thought was at first directed prevalently to the objective knowledge of the world and to the construction of metaphysics, and only through this theoretical research, stimulated by error and by the persistence of an ever more difficult and complex problematic, turned toward a more reflective and mature knowledge of itself, of its possibilities and of its limits.

The problem of knowledge is identified in the very earliest Greek philosophy in the antithesis to which the cosmological researches had led, between an external and superficial knowledge of nature, proper to immediate experience, and the deeper knowledge which thought is able to attain (φρόνησις, λόγος). The δόξα or opinion, proper to pure experience, and the ἀληθής, which alone can be attained by the effort of thought seeking to grasp the principle of nature (ἀρχή φύσεως), summarize the terms of a problem which will constitute the substance of Platonic speculation, and through it will remain perpetually alive in the history of the problem of knowledge. This epistemological dualism, to which reflection on the two fundamental forms of human knowing, sense and intelligence, naturally inclines, is present, if with a different meaning, both in Heraclitus and in Parmenides, as well as in the early atomists. The emphasis on the value of rational knowledge in the face of the illusions of experience is very strong in the Eleatic school. According to Gomperz and Burnet, Parmenides was in fact led to the position of one and identical being not by naturalistic concerns, but by the demands which logical thought makes or discovers in the concept of being: which, by its pure simplicity, excludes from itself its opposite (limit, nothingness). Thus in the Parmenidean conception there was an epistemological assumption of immense scope, namely the realistic-ancient value of human thought and of its rational demands. These, clarified in the principle of identity and contradiction, were made by Zeno to prevail with extreme logical rigor, as the sole and absolute criterion of truth. A similar position was, however, already implicit in the Heraclitean λόγος, understood as the rational cosmic principle which underlies things, as it were the objective rationality of the world, and is also the objective norm of our thought. To these epistemological positions of high intuition there does not correspond in the pre-Socratics an equal metaphysical elaboration. Their psychology (Aristotle makes an exception with difficulty for Anaxagoras’ νόμος) is in fact distinctly sensistic in orientation (Aristotle, De an., I, 2 entire). Even for Parmenides himself thought depends solely on the conditions of corporeality (frg. 16); and Empedocles’ principle has a thoroughly materialistic meaning, susceptible of quite another interpretation in a spiritualistic conception, that «the like is known by the like», i.e. the object by means of an analogous physical predisposition existing in the subject: ἡ γνώσις τοῦ ὁμολογίου τῶν ὁμολογιῶν (Aristotle, Met., II, 4, 1000 b 5-6; cf. De an., I, 2, 404 b 17). The metaphysical basis with a sensistic orientation remained in the pre-Socratics as a latent principle of dissolution of their epistemology. It is indeed difficult to maintain the absolute value of reason if the active principle of knowing is reduced entirely to sensation, by its nature relative and variable. Traces of skeptical relativism are thus already found in Xenophanes and Zeno, in Empedocles and Democritus: «we know nothing with truth; truth lies in the depths» (Diog. Laert., IX, 72).

It is therefore explained the affirmation and finally the prevalence of skepticism in the following critical-reflective moment of sophistry. Protagoras, reducing all psychic life to sensible perceptions, affirms that the object of perception, the sensible (τὸ αὐτὸ φρόντιον), is not the thing as it is in itself, but as it is determined in perception itself. Consequently, man, in the unstable continuity of his perceptions, is the measure of all things and of every one of their determinations, both positive and negative: νέαντος χρημάτων μέτρον ἀνθρώπους, τῶν μὲν ὄντων ὡς ἔστιν (Diog. Laert., IX, 51; cf. Theaet., 152 a; V. nuova traduzione e interpretazione del passo in M. Untersteiner, Sofisti, I, Firenze 1949, pp. 73-75). Hence the frankly relativistic concept of truth: for each person everything is true, insofar as it cannot be otherwise than as it appears in his perception, but everything can at the same time be called false, insofar as the representations of perception have no absolute value (cf. Theaet., 160; Sextus Emp., Pyrrh. Hyp., I, 217-19). More decisively skeptical is the attitude of Gorgias of Leontini, who pushes Zeno’s dialectic to paradox. «Nothing exists; if anything existed, it could not be known; and if it could even be known, it could not be communicated to others» (Aristot. [ps.], De Gorgia, cap. 5). Thought can therefore not make us know reality; it reveals only itself (cf. Sextus Emp., Adv. Math., VII, 77 ff.).

The extreme relativism of sophistry is overcome by Socrates through the abandonment of sensism. The concept, expression of what a thing is (τὸ ἔκστατον εἶναι), transcends sensible perception and finds its origin in the rational essence of man. The Socratic intuition, which in the end represented the metaphysical justification of the dual

The epistemological problem of early Greek philosophy is developed by Plato into a system. True and scientific knowledge (ἐπιστήμη and νόησις) is not sensation nor opinion, but rather the apprehension of the immutable being of things (Resp., V, 476 ff.; Phaed., 66 a). Such cannot be the object of perception as it is given in the phenomenal world of cosmic becoming. A realm of contingency and relativity, the corporeal world cannot contain the immobile eternity of being, truth, and science. Authentic being belongs instead to an immaterial and ideal world, of which corporeal things are a participation (μέθοδος) and imitation (μίμησις), and which thought attains within itself, beyond the sphere of sensible perception. As a quasi a priori form and object of thought, the world of ideas is known by man through a process of inner recollection (ἀνάλυσις) and almost a return to a primitive spiritual intuition (Phaed., 72 e; Meno, 86 a ff.; Phaedr., 247 c-e).

The psychological-metaphysical structure in which Plato organized the theory of ideas remains largely precarious: the objective division his doctrine entails between sense and intelligence, and the absolute transcendence of the idea, neglect a profound reality of human knowing and open the way to rationalism. Moreover, the spiritual world, fragmented into the multiplicity of ideas subsisting in themselves, is unable to fulfill the demand for absolute metaphysical unification which Plato nonetheless sought. Yet the substantial core of his entire thought—the affirmation of the idea as form and principle of reality, and thus the term of all its motion and aspiration (ἐρωτός)—directs the problem of knowledge and, consequently, the metaphysical problem, toward the spiritualistic stance that, in its fundamental meaning, underlies Christian thought.

Between Plato’s spiritualistic inanimateness and the sensism of the pre-Socratics stands Aristotle’s epistemology. Defining the nature of knowledge as the “formal assimilation” of the knowing subject with things (De an., II, 12, 424 a 18), Aristotle, consistent with his doctrine of the soul as the substantial form of the body, rejects Plato’s objective transcendence, locating the object of intellection (form, idea, concept) within the very empirical reality from which sensible representations arise to the soul through a process both passive and active. As with Plato, so too with Aristotle, science has as its object the universal and the necessary (Met., X, 8); but since the intelligible in material things exists only potentially, the grave problem of the origin of the idea also arises for him. His solution is solidly naturalistic, maintaining the absolute dependence of intellectual knowledge on sensible representations (De sensu et de sensato, 6, 445 b 16-17; De an., III 8 entire) and rejecting any actual a priori in thought: “intellectus animae... nihil est actu eorum quae exstant, antequam intelligat” (De an., III, 4, 429 a 24). Yet a residue of Platonic apriorism remains in Aristotle, inasmuch as the active principle of the idea, which he is compelled to admit to overcome the intrinsic potentiality of the intellect—the νοήσις ποιητικός or active intellect—does not seem entirely freed from the Platonic realm of transcendence (cf. De an., III, 5). Human intellectual knowledge is thus, in Aristotle, directed toward the concrete world of experience (not the Platonic world of self-subsistent ideas), yet the productive principle of such knowledge appears to remain beyond the human subject. In the doctrine of the νοήσις ποιητικός as something divine (ἐκεῖνος: De gen., 11, 3, 736 b 27-28; ἐκεῖνοι: De an., I, 4, 408 b 29)—which produces the intelligible in the soul—there persists, as indeed already in Plato, the specific problem of modern epistemology, namely the problem of the a priori of thought.

Both Plato’s idealism and Aristotle’s tempered version are substantially abandoned in the great schools of the Hellenistic period. For the Stoics, sensation is the sole source of all our knowledge, and the concept is merely a mental synthesis derived from representations (cf. frg. 60-66; Diog. Laert., VII, 61). The Stoics thus emphasize the connection already highlighted by Aristotle between sensation and thought, but fail to preserve the true universality of the concept. This empiricist tendency hardens into rigid sensism in the school of Epicurus: all our knowledge ultimately reduces to sensation understood as the passive reception of images. The concept (πρόληψις) is merely the association of images preserved in memory. Both Stoics and Epicureans explicitly address the question of the criterion (v.) of truth, which the former locate in a special persuasive force inherent in true representations (cf. frg. 60, 63; Diog. Laert., VII, 46-54) and the latter in the evidence that accompanies every actual sensation (Diog. Laert., VII, 31-34). Yet any metaphysical interpretation of knowledge is abandoned, and indeed could find no place within their essentially materialistic conception of knowledge.

Stoicism and Epicureanism were, in their own way, forms of dogmatism, yet they carried within themselves the dialectical premises of relativism and skepticism. This, already alive in the Second and Third Academy, is vigorously and acutely defended by Pyrrho: the manifold and insurmountable relativity that affects knowledge both from the side of the subject and the object (“we know only our affections”: cf. Pyrrh. Hyp., I, 38 ff. [where the doctrine of the ten “modes” or grounds of the relativity of knowledge is expounded]; and Diog. Laert., IX, 69-70); and the vicious circle (διάλληλος τρόπος: Pyrrh. Hyp., loc. cit., 164 ff. [where also the five “modes” of Agrippa]; cf. Diog. Laert., IX, 88-89) that ensnares the logical process of demonstration, necessarily lead the sage to suspend all judgment or pronouncement on things (ἐποχή). A careful record of the subtle critique that skepticism directed against contemporary Greek schools (a critique of undoubted historical value for having brought into sharper relief the internal difficulties of the problem of knowledge, sensation, evidence, and principles) is provided in the exposition given by Sextus Empiricus (2nd c. A.D.) in his three-book work Περὶ τῆς ἐποχῆς.

A distinctly metaphysical solution to the problem of knowledge is offered instead by Plotinus. The intellect (Νόησις), immediately deriving from the One, is the supreme unity of being and thought and thus the identity of subject and object (Enn., V, 4, 2); from it, through the agency of the World Soul, ideal form and intelligibility are imparted to the world. The human soul, the last spark of spiritual light enclosed in matter, contemplates in things the intelligible forms derived from the supreme Intellect, to whose spirituality it itself partakes; and it can moreover, through an interior mystical return, intuit these ideas directly within itself. The ontological-rational unity of the world in the One and in the Νόησις is thus, for Plotinus, the explanatory principle of knowledge: the Νόησις is like the absolute and divine a priori of human thought.

These metaphysical motives, corrected in a Christian sense—that is, freed from a monistic perspective—also constitute the substance of Augustinian epistemology. Two problems, moreover, intimately connected, Augustine felt most keenly, influenced on one side by the Academy and on the other by his Neoplatonic formation: the problem of certainty and that of the eternal and immutable value of truth. For both, with a modern critical attitude, he seeks a solution starting from the immanent experience of the subject: “Noli foras exire, in teipsum redi, in interiore homine habitat veritas” (De vera relig., 39, 72). Indeed, in every positive act of thought, and thus even in doubt, there is immanent the certainty of our thinking and the very value of truth (De civ. Dei., XI, 26; De Trin., X, 10; Contra Acad., II, 9). For one does not doubt nor seek the truth unless one already knows what it is. The idea of truth thus reveals an intrinsic objective necessity (which becomes more evident in the universality of metaphysical principles), one that transcends the individual, contingent, and mutable human subject, prone to doubt and error: “nisi supra mentem humanam essent [rationes aeternae], incommutabiles profecto non essent” (De Trin., XII, 2). Augustine therefore holds that the grounding of our thought in the absolute plane of truth can only be explained by a union of our intellect with the Absolute Reason: this is the “light” by which every truth shines in the soul (Sol., I, 1; De magistro, III), the source of all ideal values that man perceives in things; and it thus plays, in Augustinian epistemology, a function analogous—though not metaphysically precisely determined—to that of the *nous* in Plotinus. Consequently, in Augustine too, the absolute *a priori* of human thought cannot be fully contained within the imagination of the individual subject; it is a divine principle, yet one that, unlike the Neoplatonic Intellect, has with human intelligence a relationship of transcendental exemplarity and causality.

As a metaphysical interpretation of certainty, Augustinian doctrine passed to much of Scholasticism (cf. St. Anselm, *Prosl.*, ch. 14; St. Bonaventure, *Quaestiones disputatae de scientia Christi*, ed. Quaracchi, V, 17, 22–27; R. Bacon, *Opus maius*, III, ed. J. H. Bridges, Oxford 1897, p. 47; G. Peckham, *Tractatus de anima*, ed. Firenze 1928, ch. 3). As in every other problem, so too in that of certainty, Scholasticism presents a varied range of tendencies (well-known are the skeptical and phenomenalist attitudes, with denial of the principle of contradiction and causality, in Nicholas of Autrecourt: cf. H. Denifle and A. Chatelain, *Chartularium Universitatis Parisiensis*, II, pp. 576–80), which it is impossible even briefly to summarize here. These tendencies are most evident in discussions of the problem of universals (v.): the same problem, in essence, that had been central in Greek philosophy from Socrates to Aristotle, and which then, in realism, conceptualism, and nominalism, presented the same enduring solutions already seen in ancient philosophy from Plato to Epicurus. Medieval Scholasticism also pursued deep inquiries into the nature of truth, certainty, and faith, alongside psychological questions about the conditions, causes, and modalities of certainty.

The most complete and careful epistemological synthesis is undoubtedly that of St. Thomas Aquinas. It presents itself as a harmonious valorization of the vital elements contained in the epistemologies of Plato, Aristotle, and Augustine. It is not easy to summarize in brief points the vast contribution made by St. Thomas to the theory of certainty. Defining certainty as “the assimilation and union of the knower and the thing known” (C. Gent., II, 77; De ver., II, 1), which is achieved through an intentional representation (I Sent., d. 36, q. 2 and 3), St. Thomas reaffirms the substantial distinction between sensitive and intellectual knowledge: the concept intrinsically transcends, both from the side of the proximate knowing principle (the faculty) and from that of the object, the sensible representation (cf. Sum. Theol., 1°, q. 50, a. 1; q. 57, a. 1 ad 2; q. 75, a. 2; q. 85, a. 1; 1°-2°, q. 31, a. 5; 2°-2°, q. 8, a. 1). Nevertheless, every one of our concepts, directly or indirectly, derives from the objective contents of sensation. This, already a fundamental principle of Aristotelian epistemology, is also, from a phenomenological standpoint, the keystone of the theory of certainty in St. Thomas (cf. Sum. Theol., 1°, q. 84, a. 7). Thus, Platonic innatism is definitively abandoned: the human intellect, “a spiritual form in matter,” has no direct intuition of spiritual objects (ideas), but draws from the world of experience the universal; however vast the field of science, it cannot extend beyond the demands and postulates of sensitive knowledge (ibid., 1°-2°, q. 3, a. 6). The strict and indissoluble functional-objective continuity of thought with sensibility grounds the objectivity and concreteness of intelligible values and of the entire process of intellectual knowledge. But since intelligible values are not actually present in the data of sensation (sensation is not the “total and perfect” cause of intellectual knowledge, but rather the “matter of the cause,” inasmuch as it is through sensation that what contains intelligible values is given: cf. Sum. Theol., q. 84, a. 6), St. Thomas too resorts to an immanent activity within thought, the “agent intellect,” as the active principle of the intellectual idea.

Another important point in Thomistic epistemology is the appeal to the self-reflection of thought as a critical method by which the intellect becomes conscious of its nature and function and thus attains certainty of truth as the intentional “conformity of the mind to things” (cf. De ver., q. 1, a. 9; q. 10, a. 12, ad 7; *Perih.*, I, lect. 3, n. 6).

In Renaissance philosophy, noteworthy for its keen insights, is the epistemology of Campanella, who reaffirms, against Telesio, the irreducibility of certainty as consciousness to the physiological fact of sensation, and, together with St. Augustine, finds in the consciousness that the self has of itself (“sensus inditus”) the fundamental identity of being and knowing (for the self-conscious subject, to know is to be), and the intuitive experience of certainty (cf. *Universalis philosophia*, I, 32).

In modern philosophy, the problem of knowledge is initially felt as an epistemological problem of the true scientific method (Galileo, Bacon), but soon acquires its full gnoseological-metaphysical significance (Descartes, Locke, Kant), assuming in some currents a totalitarian function with regard to the conception of reality and thus, without doubt, of philosophy itself.

Descartes, inasmuch as he bases the certainty of the self-conscious subject as the foundation of science and philosophy, expresses the most fundamental tendency of the modern spirit, in contrast to the prevailing current of ancient and medieval philosophy, which was oriented toward subjectivity and immanence. But in Descartes, while the appeal to the immanence of the thinking subject ("cogito ergo sum": Discours de la méthode, part 4; Meditations, I) is sufficient to resolve the initial problem of certainty, the integral problem of objectivity—namely, the conformity of our sensations and our thought with reality—finds its solution only in the transcendent Principle, God, as the first cause of both reality and thought. The gnoseological criterion that Descartes discovers in the "cogito" ("what we clearly and distinctly perceive") objectively, the inclusion of one idea in another, of the predicate in the subject, of the "sum" in the "cogito," does indeed ensure certainty, but only within the subjective sphere of the *res cogitans*. The recourse to God (whose real existence Descartes believes he can find in the thinking and doubting subject: *Discours de la méthode*, loc. cit.) frees the subject from immanence and secures the ontological foundation of objectivity, since God is posited as the metaphysical center in which being and thought are identified, and as the Principle from which both the world and human reason derive. Hence the Cartesian "rationalism," according to which human reason carries within itself the norm, and in part the very content, of certainty, truth, and objectivity.

Descartes' rationalism, which in its ultimate ontological reasons was substantially in line with ancient thought, found its most significant developments in Malebranche, Spinoza, and Leibniz. For Malebranche, human knowledge is the intuition of divine ideas. Since material reality cannot act upon the spirit, and on the other hand the human spirit is not originally and by itself an accomplished act of knowledge, Malebranche concludes that the intelligence can attain its object and its ideas nowhere else than in its very principle, in God. This is an absolute aprioristic gnoseology that separates intellectual human knowledge from the world of empirical reality (whose existence is admitted only on rational principles), with the aim of transferring it to the plane of absolute objectivity. Malebranche accentuated the Cartesian dualism; Spinoza resolved it in the monism of the single Substance, which is the fundamental identity of God and the world. Knowledge is thus viewed from the perspective of absolute immanence: thought is a necessary mode of the Substance, which follows and reflects in parallel the other of its modes of being, extension. As such, knowledge is absolute truth, and error is merely a moment or lower degree of knowledge (cf. *Ethics*, part I, props. 14, 21; part II, props. 1–6, 35). Analogous, in a certain respect, though substantially different in its dualistic conception, is Leibniz’s gnoseology. Being, divided into an infinity of monads, is in itself radically conscious. Each monad, by virtue of its spiritual and representative substance, reflects the universe in varying degrees of clarity and distinctness. The harmony that the supreme Monad, God, has "pre-established" between the representative act of the individual spiritual units and the reality represented explains at once the objectivity, unity, and universality of knowledge; the pre-established harmony thus serves as the objective *a priori* of knowledge and thought.

Yet the Cartesian appeal to the self-conscious subject, together with the principle of the subjectivity of immediate experience (cf. *Meditations*, VI), also developed in a direction opposite to rationalism, namely, toward empiricism. In Locke, the epistemological problem is explicitly posed in terms that anticipate Kantian formulations (it is well known that Locke’s *Essay* was known to Kant) as a prerequisite for any metaphysical use of thought. In his *An Essay Concerning Human Understanding*, he sets out "to investigate the origin, certainty, and extent of human knowledge"; "the limits between opinion and science," in order to "discover the powers of the understanding, how far they reach, to what things they are proportioned, and where they fail" (I, 1, §§ 2–4). Indeed, "in the attempt to range over the vast ocean of being, the human mind extends its inquiries beyond its capacity, whence arise insoluble questions and disputes, fit only to confirm men in doubt and skepticism" (ibid., § 7). Consequently, the first step toward seriously addressing the questions to which the intelligence is inclined is

BIBL.:
R. Descartes, *Dissertatio de methodo*, Amsterdam 1650, p. 28, with the well-known passage "Ego cogito, ergo sum," Rome, copy from the National Library.

To take a view of our understanding, to examine our faculties, and to see to what things they are suited.” Locke’s gnoseology is therefore, in its aims, a science of the possibilities and limits of human thought. Locke carries out his investigation by adhering to the pure psychological-genetic method of mental analysis and resolution (later pursued with solid results from a psychological standpoint by Hume, Bentham, and Stuart Mill), while completely neglecting metaphysical inquiry into the nature and absolute conditions of thought. The very method of Locke’s research thus inclined toward empiricism, which in human consciousness sees nothing more than a more or less complex and stable organization of representations derived from experience by consciousness (II, 1, § 4). There are no innate ideas or a priori objects in thought: sensation and reflection (as internal perception of the experiences and psychic states of the subject) are the sole source of all our representations. Simple relations and syntheses of representations bring concepts (“tree,” “substance”) into being, which therefore have no representative value regarding the essence of reality.

Locke’s gnoseology, while representing an appropriate reaction to every form of innatism, strengthens in the current life of English philosophy the empiricist-immanentist principle (consciousness is limited to our ideas and cannot transcend them in extension or perfection, ibid., III, § 6). This principle is developed into systematic conclusions in Berkeley’s immaterialism, according to which consciousness is not the apprehension of a reality external to the spirit (material world has no existence in itself; its being consists in experience: “Principles,” § 3), but rather a divine impression of ideas in the human mind. In Berkeley (whose system represents the convergence of Locke and Malebranche), empiricism thus borders on and in a sense coincides with an absolute objective apriorism (transcendent, not transcending). God, in fact, serves as the supreme objective consciousness whose ideas (understood not merely as concepts but universally as representations of any real object) are present in every human mind (in every finite spirit) and thus account for the unity of the representation of the world and the universality of thought.

Empiricism reaches its extreme consequences in Hume. The fundamental form of consciousness, at the source of all our knowledge, is the “impression,” the strongest, immediate, and original state of consciousness. From impressions derive the “ideas,” which are like the continuation and echo of impressions in consciousness. Hume attributes the rise of ideas to two faculties of the mind: memory and imagination. Memory is pure reproduction, while imagination is a spontaneous productive function that forms and transforms ideas through an active process of analysis and synthesis, association and dissociation (Treatise of Human Nature, I, part 1, section 3). In this process, imagination does not always follow its own free course of production: intrinsic links and relations exist among ideas, causing them to spontaneously tend to unite in natural associative bonds. Through these relations, the human spirit easily passes from one idea to another; it moves from the present impression to the idea or ideas habitually linked to it (op. cit., I, part 1, section 4). On this psychological basis, Hume constructs his phenomenalism, seeking in the pure associative structure of experience (where it makes no sense to speak of different planes of depth and value) the origin of the fundamental ideas of substance, self, and cause. No original impression corresponds to the idea of substance: it is the mere “substratum” that imagination subjects to a stable complex of “coexisting” ideas. This applies both to material substance and to spiritual substance, the self: the impressions of internal experience, no matter how deeply analyzed, yield only phenomena and states of consciousness, never the self as a substantial principle. As regards the reality of experience, the self is nothing more than the total complex of states of consciousness (op. cit., I, part 4, sections 2, 6). Hume thus introduces the phenomenalist principle into the self, dissolving it as a metaphysical principle; “esse est percipi” is understood in the strictest sense as the identity of being with perceiving itself.

investigandae:
DIOPTRICE,
ET
METEORA.
Ex Gallico transita, & ab Auctore perlecta, veritijque
in locis emendata.

AMSTELODAMI,
Apud Ludovicum Elzevirium.
Anno 1631.
Cursus priorum.

(photo Enc. Catt.)
CONSENZA - Title page of the Specimina philosophiae by R. Descartes, 2nd ed., Amsterdam 1650 (1st ed. 1644). Latin version by Stefano de Courcelles revised and corrected by the author. - Rome, copy from the National Library.

As for experience. Finally, “causality,” as a necessary derivation between cause and effect, cannot be founded: not a priori, since there is no relation of identity between the idea of effect and that of cause (one can well conceive the beginning of an existence without including the cause in it); not a posteriori, because every original impression of experience, whether external or internal, yields only “succession” of facts, not their very difference (cf. Treatise, I, part 3, section 14). The idea of causal connection arises solely from associative habit that binds together two phenomena constantly conjoined in experience: it is a psychological idea rooted in a subjective inclination of the spirit (feeling), not a real relation (op. cit., I, part 3, sections 2-4, 14). Hume’s negative critique of the three fundamental ideas of metaphysics led him (at least in an agnostic sense) to reduce the real to phenomenon: experience as a series of phenomena and conscious representations is the only reality of which we can be certain, without knowing how these phenomena relate to the self and the source of being. The immanentist principle, with its improper conflation of the idea as a subjective form with its object and the ultimate reduction of the latter to sensation as a mere fact of consciousness, thus culminated in the subtle human critique, of exceptional historical significance, of metaphysical skepticism.

Kant, with the very intent of remedying skepticism and overcoming both Humean empiricism and rationalism, takes up the problem of consciousness anew and, with the critical transcendental method, steers it in a new direction: the investigation of the structure and a priori forms of our means of knowing. The great Kantian elaboration, developed primarily in the first Critique, culminates in a conception of consciousness that is, in its specific form, new—even if some of its aspects were foreshadowed as early as ancient sophistry. For Kant, the concept of consciousness as the “assimilation” of the subject to a given and predefined reality as object is definitively abandoned.

c. is human apprehension of objects, but insofar as these objects are posited in act by the very process of construction. C. is therefore a “synthesis a priori,” that is, the constructive activity of the subject that imposes upon the matter of knowing the forms of its own subjectivity (“intuitions” of sense and “categories” of the intellect), which are in it prior to all experience and transcendental conditions of experience itself: space and time, and general concepts (existence, substance, causality, etc.), even though they apply to a matter that lies beyond the subject (realism), do not express the transcendent being of the object but universal objects of the subject (transcendental idealism). In this way Kant intends to account for the universality of scientific knowledge by deriving, in its formal structure, from the subject itself. Such a subject, principle and center of the representations of objects and hence of c., is for Kant, in the final analysis, not the empirical individual subject (which is itself given and constructed by experience), but the “consciousness in general” (überhaupt) or the transcendental unity of apperception, the “I think.”

Kantian epistemology leads to the impossibility of the metaphor that is precisely the putative object of metaphysics. The objects of metaphysics—self, world, God—are valid only as ideal terms of unification of experience: they are “a priori forms” of reason to which no intuition in experience corresponds. The merit of the Kantian critique, beyond marking the condemnation of every rationalism that claims an a priori metaphysics, was to bring to full evidence the intrinsic character of activity in c., and thus the demand in the subject for an “a priori” as condition and form of this activity. A problem, it may be said, fundamental for every adequate attempt to explain c., from Plato onward. But the Kantian “a priori,” as objective precondition, went beyond the limits permitted by the phenomenology of human knowing, which attests to the derivation of the object from experience. Moreover, by positing the “I” or “consciousness in general” as the condition of c. in its universality, Kant, while transferring the “a priori” beyond the individual human subject, confined it within a sphere of abstract objectivity that no longer implied any causal relation with the transcendent. Thus were laid the premises for an interpretation of c. in an immanentist-idealistic sense.

The solution of post-Kantian idealistic conceptions (which are no longer simple “critiques” of c. but metaphysical developments of the postulates of criticism) consists in having elevated to an absolute metaphysical position the Kantian “I think.” In Kant, “consciousness in general” was the supreme principle of the phenomenal representation of the world and nature, that is, of their organization as objects in human c.; the “transcendent I” of the idealists (“Subject” in Fichte, “Absolute” in Schelling, “Idea” in Hegel, “Self-concept” in Gellert) is instead the immanent I of c. in an immanentist-idealistic sense. The principle of a single reality is thus established. Particular emphasis is given to the Hegelian system for its absolute immanentist-dialectical conception of the real and the vast influence it exerted on Italian idealism (Spaventa, Croce, Gentile [V. ATTUALISMO]).

For Hegel, Spirit or Universal Idea is the true concreteness of being; the forms by which it internally determines and unfolds itself are at once the forms and categories of reality. It is the “Idea” that, through its immanent rational process, gives consistency to the real, which in this way resolves itself into the very becoming of Spirit (historicism). Dialectic is the essential structure of the spiritual process, and contradiction the inner soul of dialectic: every position, moment, or category of spirit and hence of reality, by the immanent instability that pervades it, naturally tends to resolve itself into negation, which in turn posits itself as the principle of a further dialectical process, and so on endlessly in the rhythm of spirit. Beyond the apparent multiplicity of dialectic and history is the fundamental unity of spirit, synthesis of all opposites (absolute-relative, infinite-finite, universal-individual, substance-accidents, etc.), which it nourishes with its spiritual source. The gradual forms by which dialectic unfolds in the world follow the ideal process of Spirit, which, extrinsically manifesting its original identity in the necessity of nature, arrives through this at the clarity of absolute self-consciousness.

C. is then, in Hegel, the process by which the “Idea,” having overcome the antithesis of objectivity and subjectivity, posits the identity “Encycl., §§ 224-225.” It is theoretical activity by which the idea negates the “universality” of its subjectivity by embracing within itself the world as content (ibid., § 225). But since the world is in itself and for itself the “Idea,” and it itself “produces its reality through activity” (ibid., § 235), knowing is the very doing of intelligence as theoretical spirit. C. is therefore absolute realizing activity, absolute positing of objects. As is clear, in Hegelian monism c. no longer essentially counts as the act of individual thinking subjects; it is the apex of the absolute dialectical process, and thus its belonging and referability are infinite. Its meaning is radically different from that which it had in the traditional dualist conception. Unified as individual human subjects within the Absolute Subject as moments of its becoming and cosmic realization, they lose their personal autonomy and with it the authentic value of subjects as such. Human thought, while thus apparently elevated to absolute significance, by its substantial identity with the single spiritual principle of the world is swept up in the irreversible process that the “Absolute” accomplishes in history.

Idealism had attempted to rationalize experience within the transcendent absolute. For positivism, however, experience in its empirical reality is the only authentic value of reality and of which our most solid knowledge is constructed; and vain is any metaphysical inquiry that pretends to go «beyond» experience. For Taine and Ribot, consciousness is a mere «epiphenomenon» of a form of natural reality, namely the physiological facts of the nervous system; and the spirit is nothing but a flow of sensations and perceptions. For Ardigò, consciousness is the expression of an original undifferentiated reality, a synthesis of the physical and the psychic. A similar conception is found in F. Lange and W. Schuppe, for whom consciousness is the pure psychic aspect of a single fundamental reality, unknown in its profound determination. Spencer sought the solution to the problem of consciousness in evolution, attributing to its genetic processes and hereditary transmission the emergence and stabilization of the forms of consciousness and thought, which then in the individual appear as original and a priori structures; even though Spencer acknowledged, beyond experience, an absolute reality in itself unknowable. The value of experience as such is emphasized by E. Mach and R. Avenarius, who highlight the primitive unity of «experience» by which the dualism of object and subject, reality and consciousness, is resolved and overcome; and by Ch. Renouvier, who reduces positivity to the phenomenal world of consciousness, even though this phenomenal world is open to a possible overcoming of itself through the value that the subject represents as will. With Condillac, and then with Diderot, Helvétius, positivism culminates in pure materialistic sensism, whereby the metaphysical problem of consciousness no longer subsists, as it is an adequate product of matter at the highest degrees of its organization.

Yet the very Hegelian system had given rise, through its «left-wing» developments, to materialistic trends. Idealism, in fact, due to its absolute immanentist resolution, is already on the borders of materialism. Feuerbach, taking up the position of traditional materialism, sees in consciousness and the idea an externalization of nature, an arcane and profound reality in which man, with all his spiritual being, has his roots. From this fundamental presupposition, and by inserting into the materialistic schema the Hegelian dialectic and its historicist conception of the real, dialectical materialism as constructed by Marx. Consciousness is not an ideal and metaphysical «prius» of reality (Hegel), but rather a naturalistic product of II. Eternal matter, without beginning or end, has through dialectical leaps arrived at the brain, of which consciousness is a property; this, while representing a radically different aspect from extension, is nonetheless in matter as its own and highest property, and does not transcend II. It is, in essence, the «subjectivity» that accompanies the «objective» processes that take place in the brain. But what, beyond the generic materialist basis, most characterizes the theory of consciousness in Marx and the later theoretical exponents of Marxism (cf. G. A. Wetter, Il materialismo dialettico sovietico, Torino 1948, especially ch. 5, pp. 335–89) is the interpretation of consciousness itself in terms of the social fact. Consciousness, in fact, as Feuerbach already held, properly belongs not to the individual but to social man. The modes and forms of consciousness and the values that are actualized through it are therefore functions of man’s social being and, consequently, of all the factors, causes, and conditions on which society depends. And since society, its forms, and its developments are essentially functions of economic facts (labour, wealth, modes of production of wealth and the consequent economic relations between classes), consciousness and its values ultimately depend on economic facts and values. It is in this its historical-social-class concreteness, according to Marx, that human consciousness is internally qualified and assumes its specific objectivity and meaning. It is evident that this objectivity is only relative in meaning. In reality, nothing is absolute except the dialectical process of the world and of consciousness itself; whereas every single moment and degree of consciousness is unstable and relative, both in relation to its object in becoming and to the conscious subjectivity itself, which is also in dialectical becoming within the world and with the world. Categories and concepts are immersed and channelled into social historicism and thus into economic praxis: truth and falsity are always conjoined in every idea, category, fact, or reality, by virtue of the dialectical process that submerges some aspects, brings others to the fore, and then destroys these again in a perpetual rhythm. The only absolute aspect that Marxism recognizes in consciousness (but in this it is already entangled in contradiction) is that it has discovered and recognized the laws of the dialectical process.

Alongside movements that were more directly influenced by German idealism, the spiritualist current reasserted itself, particularly in Italian thought of the 1880s. Bonalupi, in the ontological-gnoseological identity of self-consciousness as a spiritual act and in the infinite dimensions it potentially encompasses, founds the affirmation of the transcendent Principle. Galluppi, in line with St Augustine and Descartes, seeks in self-consciousness the first reality, the «shore of existence»; and, avoiding on the one hand empiricism and on the other Kantian transcendentalism, he grounds the categories of being—first substance and cause—in the concreteness of experience, while acknowledging the active and mediatory function of intelligence that actualizes them through judgment. Rosmini, aiming to valorize in a Christian sense the demands of criticism, sees in the idea of being the unique and supreme form of thought, by which experience is organized into intellectual consciousness. This is an ideal form, not pure subjectivity; almost a perennial intuition of thought, a universal value, which presupposes as its foundation the being that is God Himself. The idea of being is therefore at once the objective reason for the spirituality of the human subject and the a priori condition of all intellectual consciousness. Gioberti attempted to overcome Rosmini’s ideal being by identifying it with the first «Being» as the ontological principle of the world and of the «existing». The human spirit is thus, in itself, in the immediate intuition of being and therefore of truth: a fundamental intuition that is like the «a priori» of all our consciousness and illuminates from above even sensible perception and consciousness.

Recent intellectual movements, though largely influenced by the immensely idealist tradition, sometimes connect directly to criticism by developing one or another of its conflicting motifs. They link back to the negative outcome of Kantian criticism and its declared impossibility of metaphysics, giving rise to recent anti-intellectualist currents that share the conviction of the constitutional inadequacy of conceptual thought to dominate reality and resolve problems. These include neo-positivism, various forms of relativism and agnosticism, pragmatism (James), intuitionism (Bergson), and earlier traditionalism. These movements either renounce metaphysics in the strong sense of the term (turning instead to life, instinct, or existence) or attempt to reach it by other paths beyond or short of logical-rational thought processes. In this direction, developments have occurred that highlight the positive aspects contained in Kant’s *Critique of Practical Reason*. Blondel’s actionism (and other analogous currents), without detracting from their originality and novelty, can be considered a metaphysical valorization of the demands that Kant already recognized in action and moral problems through his "postulates." In existentialism, the problem of knowledge assumes a secondary role, as it is subordinated to supposedly more fundamental tendencies such as "anxiety," "situation," or "choice."

In the reductio ad absurdum of modern thought as absolute self-consciousness and immanence, and in its failure in the historical test, U. Spirito discerns the reasons for a new spiritual stance: "problematicism." It asserts itself as a theoretical position of pure recognition of the problem encountered at the foundation of every thought process. Problematicism is not skepticism, for although it admits the possibility of doubt extending to all theoretical and practical values, it remains a commitment to research, "capable of perceiving the radical inadequacy of a self that does not know how to possess itself or reality, and to which nothing remains but to confess the consciousness of its limit and the hope of transcending it" (*Il problematicismo*, pp. 51-52).

The most strictly Catholic thought of the last century, expressed in the Neoscholastic movement, has devoted extensive studies and research to the problem of knowledge. In general, it can be said that the manifold solutions do not present substantial differences, as they all, by different paths, arrive at the conception of knowledge as an "objective assimilation"—albeit imperfect—by a spiritual, participated, and finite subject of a reality independent of it in its being. This reality derives its knowability and intelligibility from Transcendent Reason, the principle and cause of reality itself and the absolute identity of being and thought. While recent research has produced many valuable studies concerning the metaphysical deepening of knowledge and the critique of epistemological systems—especially Kantianism and idealism—numerous investigations have also addressed the so-called "critical problem," namely the search for a critically valid path to secure the value and objectivity of knowledge in general. Essentially a methodological problem, and therefore of unquestionable importance, the critical problem has thus received numerous formulations and solutions, though sometimes of relative value in relation to the metaphysical problem, which remains the principal requirement of a theory of knowledge.

The epistemology of the early Neoscholastics (Balmes, Liberatore, Cornoldi, Sanseverino, Farges, Tongiorgi, Palmieri, and later Remer, Gredt, Hugon, etc.) was primarily anti-skeptical and anti-Kantian. For them, in general, the critique of knowledge has a relatively modest role in ascertaining and discerning true knowledge based on the first principles of metaphysical-logical order and the criterion of evidence (v.). The more radical problem concerning evidence itself was not sufficiently discussed, even if perceived (Balmes): namely, what its metaphysical foundation is; how to discern "true" evidence; and whence the frequent subjective character that accompanies II. A partially new approach was attempted by Mercier, who shifted the starting point by establishing the first certainties in the objective value of principles of ideal order.

The various "critiques" of knowledge that followed—numerous in the last fifty years and sometimes undeniably original—can be reduced to two general tendencies (though it must be noted that this classification is inevitably somewhat approximate and should not be understood as a strict antithesis, given the substantial agreements that often exist among various authors beyond their predominantly methodological differentiations): the first, which is based on experience and from its analysis draws conclusions about the meaning and value of knowledge; the second, which seeks to solve the epistemological problem by starting from the objective content of intelligible values (concepts and principles). Since experience is manifold (sensitive, intellectual, subjective, objective, intuitive, theoretical, practical, mystical, religious), the first tendency has given rise to various schools. In general, the fragmentary, passive, and contingent character of human experience is emphasized, leading to the conclusion that a transcendent reality and rationality (in both epistemological and metaphysical senses) must exist as an adequate explanation of it, and thus to the apprehensive value of knowledge. Particular importance is often attributed to the experience of the self as a spiritual subject of intelligence and will, and thus in an immanent and dynamic relationship with the infinite. Among others belonging to this first tendency, despite significant differences in approach and method, are De Vries, Noël, Picard, Veuthey, Brunner, Zamboni, Padovani, Stefanini, Guzzo, Vanni-Rovighi, and Morandini. The second tendency grounds the value of knowledge either in the objective meaning of the idea of being (Lepidi, Gardeil, Roland-Gosselin, Olgiati, Garrigou-Lagrange, Jolivet) or in the epistemological meaning of judgment, whether as an expression of universal objective truth (Rickaby, Sentroul, Romeyer) or as a universal assertive synthetic function in which the objective transcendental conditions and demands of human knowledge are revealed (Maréchal).

The two tendencies of Neoscholastic thought indicated above reveal two fundamental, partially divergent attitudes: one strictly epistemological, which insists on the absolute priority of the critical moment over the metaphysical one (and consequently of the problem of knowledge over that of being), and thus seeks, through knowledge and for its sake, to reach being and metaphysics (Zamboni, Picard, De Vries, etc.); the other, which defends the priority of the metaphysical moment, in which the critical exigency itself is inserted and finds its absolute justification: the problem of knowing passes into being, which is found within being (Garrigou-Lagrange, Maritain, Masnovo, Olgiati, etc.). Between these two attitudes, a third position is emerging that does not aim to resolve the critical moment into the metaphysical one or vice versa, but recognizes a priority in their respective domains. This is to be understood in the sense of a "convergence" and mutual foundation, in that the phenomenology of knowing leads to metaphysics, but metaphysics in turn provides the ultimate foundation and meaning of the functions, structures, and contents of phenomenology (Fabro, Rahner). This position seems to correspond to the essential structure of human knowing, identified by Aristotle and St. Thomas in the "intellectual conversion" of phantasms.

2. Problems

The exceptional historical development of the theory of knowledge and the depth to which it has driven philosophical inquiry are in themselves grounds for the legitimacy of its claims and problems. Such legitimacy should not give rise to disputes, especially when one considers the centrality of the problem of knowledge, whose solution is indispensable for achieving valid theoretical knowledge of ourselves and the world, and thus for a consistent solution to the problem of life. The theory of knowledge is justified precisely as an inquiry into the meaning of experience and of integral human knowledge, primarily in relation to the question of the possibility of metaphysics—that is, of an absolute theoretical system of reality. And since human knowledge is an empirically complex fact, the theory of knowledge cannot and must not be identified with any of the particular epistemological problems; rather, it must be a methodical examination of all the substantial problems concerning knowledge.

There are partial and therefore inadequate conceptions of the theory of knowledge that must be rejected. Thus, it cannot be reduced to the abstract problem of certainty and truth. Since, in fact, the levels of human knowledge are manifold and to these correspond different kinds of certainty and truth, a solid theory of knowledge must pose the problem of truth and certainty concretely—that is, in relation to the various forms and modes of knowledge and their intrinsic meaning. Nor can the theory of knowledge be identified with the problem of the passage from subject to object (the question of the “bridge”), and thus with the problem of the existence of external reality. Such an approach to the epistemological problem betrays the gratuitous postulate of the subjectivity and immanence of experience, which underlies so many modern epistemologies too remiss toward idealistic principles. Nor is the theory of knowledge the abstract problem of error or of the criterion of truth. Indeed, the problem of error comes after the positive inquiry into the possibilities and validity of knowledge, and there are no criteria of truth distinct from the intrinsic characteristics that truth itself presents in the different objective levels of knowledge, in which it is distributed.

The theory of knowledge is the reflective philosophical inquiry into the forms and structures of knowledge, aimed at critically establishing its value and thus advancing toward a metaphysics of knowledge in general, of man, and of being. Its problems are therefore defined and organized in relation to the entire scope of human knowledge: what is the general meaning of experience; what the objects of sensory knowledge and those of intellectual knowledge truly represent—concepts, ideas, principles; what value metaphysical notions such as being, substance, cause, the self, spirit, God possess; what is the content and validity of the fundamental categories in the scientific, aesthetic, ethical, and religious orders; what is the value of the various logical procedures of deduction and induction; what meaning human thought’s historicity presents; what in any order of knowledge are the parts of the subject and those of the object in the genesis and thus in the structure of cognitive representation; what problems arise from the data of human experience; what gnoseological-ontic structure the data of experience presuppose in the subject; what, therefore, are the ultimate metaphysical conditions of experience and knowledge, and what value spirit has in the world. As is clear, a concrete solution to these problems also resolves, through a solid analytical-synthetic process, the questions of truth, certainty, error, objectivity, and the possibilities and limits of human knowledge.

Thus, the position of the theory of knowledge in its relations with other philosophical disciplines, with which it shares the material field and object of research, becomes clear. It cannot be confused with logic (understood in the traditional sense as “pure” or “formal”), which analytically establishes the laws of formal thought but ignores the question of its value as an expression and objective adequation to reality. Nor can it be resolved into psychology, which is the study of the genesis of knowledge and thought as a psychic process; although the methods of such research are an indispensable aid to epistemology. Nor, in the position and solution of its initial problems, is it a metaphysics in the proper sense, since its very task is to lead toward metaphysics by establishing the meaning of cognitive processes.

Yet, for the same reason, every theory of knowledge necessarily opens and is fulfilled in metaphysics, inasmuch as, in seeking the conditions, principles, and value of knowledge, it cannot but imply a theory of being that, grounded as a dialectical exigency by the fact of knowing, in turn serves as the absolute and metaphysical foundation of knowledge itself.

A question that in the theory of knowledge seems to present itself with special difficulty and has therefore given rise to endless discussions both in Catholic thought and in other schools is that of method. It would evidently be impossible to construct a theory of knowledge without using knowledge itself, and so a critical examination of the value of knowledge as such would seem impossible, since that value is already implicitly presupposed by the inquiry itself. In reality, the antinomy is more apparent than real, being caused by an inexact formulation of the problem. The problem of knowledge is sometimes posed in the general form “whether human knowledge has value.” Now, that human knowledge has value, for example in the vast realm of common experience and scientific certainty, is not a problem but a fact which the most immediate critical reflection of thought is sufficient to recognize and elevate to the level of theoretical affirmation, and which therefore cannot be called into question: it is not a matter of knowing whether human knowledge has value, but how far such value extends. Already St Thomas noted: “veritatem esse in communi est per se notum” (Sum. Theol., 1a, q. 2, a. 1 ad 3). The problem of knowledge offers of itself positive data which must constitute the foundation and starting point of gnoseological research. These include: the very existence of human knowledge, its history, its achievements in practice, in science, and in philosophy; the certainty which each person has of the facts of his own experience; and finally the philosopher’s reflection when he poses the problem of knowledge. To ignore these data and attempt to begin methodically from universal doubt is absurd. The very problem that imposes itself on the philosopher’s consciousness and requires a clear knowledge of what is intended and sought; and the nature of thought, which is by essence affirmation and tolerates no absolute negative state, are the most decisive condemnation of such attempts, which in any case have never seriously preoccupied the greatest thinkers and are today generally abandoned by Neoscholastic gnoseology.

The critical problem, if it is to be understood in its broadest and least pregnant expression, as a general question about the possibility for human thought of true knowledge, is radically resolved in the self-reflection of thought which perceives its understanding, its doubting, its seeking, and in this awareness—just as in every existential judgment on the facts of experience—has consciousness of its absolute conformity to reality: at least to the reality of its own experience. Nevertheless, it is one thing to reject, at the outset of the theory of knowledge, universal doubt, and to affirm or presuppose the universal validity of human reason in any sphere of objects and problems; it is another thing to affirm in general the possibility for human thought of true knowledge, and the certainty of objectivity and truth in whatever direction human thought engages its powers. For this purpose a methodical and systematic examination of knowledge and its structures is indispensable.

Therefore, while it seems necessary to reject every gnoseology that starts from unwarranted dogmatic presuppositions—for example, from the metaphysical value of concepts and judgments and of the knowing subject itself (the principle of finality presupposed as an ontological norm of the cognitive faculties)—equally insufficient are those gnoseologies which begin and develop from a single datum of experience (generally the certainty of the self-conscious subject and its character of ontological contingency), because they neglect a full examination of human knowledge in its complex organization.

The true method for a solid theory of knowledge (and this is today more and more generally admitted) proceeds from a systematic examination of knowledge, and therefore first of all from a phenomenological or objective analytical description of consciousness and experience in all its presentations (sensible, intelligible, spiritual, intuitive, abstractive), developments, and implications. This method is critically justified because it involves no theoretical presuppositions beyond the factual data of the problem. Nor is the value of critical reflection preaffirmed in the abstract; rather, the results of reflection are allowed to make themselves valid in concreto by their objective clarification within consciousness: phenomenological examination does not involve discursive procedures of reason, but is experience itself which, through the reflective process, is clarified in its content. Even the first principles, which in their formal value are the internal condition of thought, clarify their own ontological value through the disentangling of the objective content of their respective terms, as operated by phenomenology. The phenomenological description surveys the different forms, orders, structures, moments, and objects of knowledge; it investigates their objective and subjective conditions; it sees knowledge in its genesis and historical development and in its organic insertion into the integral human fact—individual and social, theoretical and practical, logical and affective, as well as psychic, biological, and cosmic. In this way it reveals the complexity of gnoseological problems and places them in their real and concrete perspective, seeking out and identifying the manifold factors involved in the fact of certainty, truth, and error; and in conclusion it avoids in the treatment of the problem of knowledge every abstraction and virtuosity.

Phenomenology does not limit itself to the data, but spontaneously passes to a higher stage, namely to problematic positions. For analysis discovers in experience contents and situations of object and subject which open up into problems—problems which arise from experience but at the same time transcend it because they do not find in it an adequate solution. The analysis of experience is thus transformed into a “dialectic” of experience itself, and to the descriptive-critical method is added the transcendental method which investigates the necessary conditions in object and subject, and if necessary beyond these, in order to explain experience.

A theory of knowledge developed according to these directives of intent and method seems necessarily oriented toward realism and transcendence. The first characteristic which it reveals in the structure of human consciousness is its intrinsic potentiality and its gradual constitution in time in function of the objective contents of sensibility. The criticism which empiricism, in agreement here with Thomist thought, has directed against the various forms of innatism in the name of concrete analysis of experience is definitive. Human intelligence has no a priori contents in act: its contents, ideas, concepts, principles, and consequently every synthesis and elaboration of them, come to be in act

dependence and continuity with the data of experience. In turn, these data function not for the autonomous victory of a “pure” subjectivity (which phenomenology demonstrates to be nothing other than a systematic abstraction), but rather for the manifold perceptual relations that subjectivity establishes with the world and reality, including its own empirical-psychic reality. The error of empiricism, arising from the insistence of a methodological process isolated to a partial aspect of experience, outside of its solid and living concreteness, was the reduction of the given to “phenomenon.” Such a reduction presents itself as an unjustified mutilation of experience, whose meaning as contact and relation with reality (even if through subjectively structured forms) is evident in the perceptual character of sensation.

Moreover, the data of experience in general, by the mere fact of being posited within an intellectual consciousness, passes over into ontological value: its very phenomenality (understood here as the “presence” of data), in the more or less dense planes of values and contents in which it is situated (from that of a simple psychic state, such as a feeling or an emotion, to the pregnant one of a personal reality that stands before us and opposes us as a hostile force), insofar as it is given in a thinking consciousness, transcends itself as phenomenon, clarifying itself in its structure as being.

The concept of being (which is at once the keystone of gnoseology and metaphysics) can thus be said to be both a posteriori and a priori. Being, in fact, does not posit itself as a positive content (being in the strong sense, as an actual act of existence determined in an essence) unless the potentiality of thought is realized in experience, and precisely to the extent of the objective intensity of experience itself. But it also partakes of the a priori insofar as it is at the center of intelligence as its transcendental relation to the absolute: the ontological structure of thought that constitutes, in itself, a radical objectivity. The objectivity of the concept of being thus has, consequently, a double foundation—if one wishes, a double meaning: as “value” (the first and most absolute value from which all other values depend), being constitutes the very essence of intelligence as the power to think the object, and is therefore a universal objectivity that is prior to and independent of contents; whereas as a concept in act, being is determined, for human intelligence, in the contents that consciousness draws from the world; and thus has an “established” objectivity that is measured by experience. Human intellectual consciousness thus reveals itself as the progressive and historical actualization of a universal potentiality that is at once passive and active, insofar as it finds in a transcendent reality (in the gnoseological sense) its ontic contents, but these contents universalize themselves in the absolute value of being, present in thought as a priori theoretical structure and radical objectivity.

The solution thus proposed (and which seems to respond to the legitimate demands of both empiricism and rationalism) explains the two fundamental characters that human consciousness has constantly revealed to philosophical inquiry, determining, at different times, the prevalence of empiricism or rationalism: on the one hand, its universality, evident in all absolute values of truth, both theoretical and practical, realized by human knowledge, from primitive and spontaneous consciousness to the most mature philosophical conceptualization; on the other, its empiricity, evident in the essential character of the historicity of thought, in its indefinite dialectical rhythm, destined to endure as long as concrete human existence endures. Universality is explained by the absolute structure that lies at the roots of thought as the relation of consciousness to being; empiricity is clarified, overall, by the becoming of experience, in which the potential structure of human thought is destined, by its nature, to actualize itself. Similarly, it is the absolute structure of thought that accounts for the general conditions of metaphysics, present in every human self-consciousness in the clarity and distinctness of the concept of being and of the first principles included in its positivity; whereas the essential reference to experience explains the difficulty, for human thought, of achieving a complete metaphysics from the standpoint of the exigencies and integral principles of being.

Phenomenology, while clarifying human consciousness in this way as a progressive adequation to an object and its necessities, on the other hand, by highlighting the character of universality and absoluteness that is conjoined with intellectual consciousness (both in its conceptualizing function and in its assertive function of judgment as unconditioned affirmation in the plane of being), poses the problem of the absolute derivation of thought. As can be seen from the historical exposition, this is the gravest metaphysical problem posed by consciousness and human experience. Kant and nearly all modern philosophy have attempted its solution on the pure transcendental plane, understood either in an objective sense (the Absolute, as the foundation of human thought as necessity and abstract rationality: Kant and, recently in Italy, Carabellese) or in a subjective sense (the Absolute, as the foundation of human thought as an infinite Subject immanent to it: idealism). But both solutions prove insufficient: the first, because an objective rationality cannot be conceived without a subjective Consciousness, as the idealists well saw; the second, because in its substantial identification of human thought with the Absolute, it does not respond, as has already been noted, to the real conditions of experience and of the human subject. The ego, in the clear awareness of consciousness, while perceiving its unity and positive personal individuality, has at the same time the unequivocal experience of its insufficiency, its dependence, its effort, its tendency—never adequately realized—toward an infinite objective actualization in truth and goodness. Thus, the ultimate answer to the problem of consciousness is to be found only in the perspective of Transcendent Rationality as supreme Subject and Object: which, as Augustine and St. Thomas intuited, serves as the metaphysical principle of human intelligence and its transcendental structure; and at the same time as the ultimate term and measure of its possible actualization.

I. CLASSICS: For the pre-Socratics V. the relevant section of Diels’ Fragmente (for the Sophists, the recent edition by M. Untersteiner, Sofisti, I, Florence 1940). Of Plato, see especially Parmen., Theaet., Respubl. (VI–VII); Phaedr., Menon. Of Aristotle, see especially De

soul; On Sense and the Sensible; Met. (IV, 3-7; XIII, 4-5); see the Stoics and Epicureans or the collections of fragments by H. von Arnim and H. Usener. For the Skeptics, see Sextus Empiricus, *Pyrrh. Hypot.* and *Adversus Math.* For Plotinus, see *Enn.* (especially V-VI). For St Augustine, see *Contra Acad.*; *De vera rel.* (from chap. 20); *De diversis quaestionibus 83* (esp. qq. 1, 45, 54); *Confess.* (IV, VII, X); *De Trinitate* (from bk. VIII); *De Civitate Dei* (VIII-XII, XIX, XXII). For St Thomas Aquinas, see *Summa Theologiae* (especially 1°, qq. 14-17, 54-58, 78-79, 84-89); *Summa Contra Gentiles* (II, 58-78; III, 33-63); *Quaestiones disputatae de anima*; *De veritate* (especially qq. 1-10); *In de anima*; *De sensu et sensato*; *De unitate intellectus contra Averroes*; *De natura verbi intellectus* (doubtful); *De differentia divini verbi et humani*; *De intellectu et intelligibili*; *De intellectu respectu universalium* (these last three are spurious but drawn from works of St Thomas). For Bacon, see *Novum Organum*. For Descartes, see especially *Discours de la méthode*; *Meditations* (with objections and replies) and the *Principles of Philosophy*. For Locke, see the cited *Essay*. For Berkeley, see, besides *Treatise on the Principles of Human Knowledge*, *Three Dialogues*. For Malebranche, see *De la recherche de la vérité*. For Spinoza, see *Ethics* (pt. 2). For Leibniz, see *Meditationes de cognitione, veritate et ideis* and especially *Nouveaux essais sur l’entendement humain*. For Vico, see *De antiquitate atomorum sapientia* (sect. 1). For Hume, besides the cited *Treatise* (I, I), *An Enquiry Concerning Human Understanding*. For Kant, besides the three *Critiques*, see also *Prolegomena to Any Future Metaphysics*. For Fichte, see especially *Grundlage der gesamten Wissenschaftslehre*. For Schelling, *Transcendental Idealism*. For Hegel, *Wissenschaft der Logik*; *Encyclopedia of the Philosophical Sciences* (especially vol. III, §§ 160-244, 377-380) and *Phenomenology of Spirit* (especially vol. I). For Schopenhauer, *The World as Will and Representation* (especially vol. II). For Hamilton, *Lectures on Metaphysics and Logic*. For Spencer, *First Principles* (pt. 1). For Stuart Mill, see especially *Examination of Sir William Hamilton’s Philosophy*; *System of Logic* (I, chaps. 3, 7). For positivism, see also A. Bain, *The Senses and the Intellect*; H. Taine, *De l’intelligence*; Th. Ribot, *L’évolution des idées générales*. For traditionalism, see V. De Bonald, *Recherches philosophiques sur les premiers objets des connaissances morales*; L. Bautain, *L’esprit humain et ses facultés*. For Marx, see especially *Zur Kritik der Nationalökonomie*. For Bonatelli, see *Pensiero e c.: La coesione e il meccanismo interiore*. For Rosmini, see especially *Nuovo saggio* and *Il rinnovamento della filosofia*. For Galluppi, *Saggio sulla critica della ragione*. For Gioberti, see *Protologia* (essays I, III, IV) and *Introduzione allo studio della filosofia* (chap. 4). For sensism, see E. Condillac, *Essai sur l’origine des connaissances humaines*; H. C. Helvétius, *De l’esprit*; A. De Tracy, *Éléments d’idéologie*; J. De la Mettrie, *Histoire naturelle de l’âme*. For Catholic thought of the 19th century, see J. Balmes, *El criterio* and *Filosofia fundamental* (I); J. Kleutgen, *Philosophie der Vorzeit* (I); M. Liberatore, *Della conoscenza intellettuale*; F. Zigliara, *Della luce intellettuale e dell’ontologismo*. For pragmatism, see W. James, *Pragmatism*; *The Meaning of Truth*. For Bergson, see *L’évolution créatrice*; *Matière et mémoire*; *La pensée et le mouvant*. For Blondel, see *L’action* and *La pensée*. For Croce, see *Logica*. For Gentile, see *Teoria generale dello spirito come atto puro*; *Logica*. For existentialism, see, among others, K. Jaspers, *Von der Wahrheit*, Munich 1947.

II. HISTORY: N. Kaufmann, *Die Erkenntnislehre des hl. Thomas von Aquin*, Fulda 1889; J. Beare, *Greek Theories of Elementary Cognition from Alcmeon to Aristotle*, Oxford 1906; E. Cassirer, *Das Erkenntnisproblem in der Philosophie und Wissenschaft der neueren Zeit*, 3 vols., Berlin 1906–56 (vol. I, 2nd ed., 1910; vol. III, 1920); D. Lanna, *La teoria della conoscenza in s. Tommaso d’Aquino* (with bibliography, pp. 291–300), Florence 1911; B. Kalin, *Die Erkenntnislehre des hl. Augustinus*, Sarnen 1920; E. von Aster, *Geschichte der neueren Erkenntnislehre*, Berlin 1921; K. Dürr, *Wesen und Geschichte der Erkenntnis*, Zurich 1924; M. Grabmann, *Der göttliche Grund menschlicher Wahrheitserkenntnis nach Augustinus und Thomas von Aquin*, Münster in W. 1924; P. Rousselot, *L’intellectualisme de st Thomas*, 2nd ed., Paris 1924; R. Kynast, *Logik und Erkenntnislehre der Gegenwart*, Berlin 1930; id., *Geschichte der Logik und Erkenntnislehre*, 1913; J. Hessen, *Augustins Metaphysik der Erkenntnis*, Berlin 1931; P. Wilpert, *Das Problem der Wahrheitssicherung bei Thomas von Aquin*, Münster 1931; A. Hufnagel, *Intuition und Erkenntnis nach Thomas von Aquin*, 1913; B. Romeyer, *St Thomas et notre connaissance de l’esprit humain*, 2nd ed., Paris 1932; G. Siewert, *Die Metaphysik der Erkenntnis nach Thomas von Aquin*, Munich–Berlin 1933; L. Keeler, *The Problem of Error from Plato to Kant*, Rome 1934; G. Zamboni, *La gnoseologia di s. Tommaso d’A.*, Verona 1934; H. O. Gardeil, *Les grandes étapes de l’idéalisme*, Paris 1935; K. Rahner, *Geist in Welt. Zur Metaphysik der endlichen Erkenntnis bei Thomas von Aquin*, Innsbruck–Leipzig 1939; J. Sauter, *Der Platonismus in der Erkenntnislehre des hl. Thomas von Aquin*, Innsbruck 1939; C. Boyer, *L’idée de vérité dans la philosophie de st Augustin*, 2nd ed., Paris 1941; J. Maréchal, *Le point de départ de la métaphysique*, vols. I–IV (extensive historical-critical study), 1912–49; G. Van Riet, *L’épistémologie thomiste* (on the theory of knowledge in neo-scholastic Thomism), Louvain 1946. Further bibliography (with special reference to journal articles) on the theory of knowledge in St Augustine, in scholasticism in general, and in St Thomas can be found in C. Giacon, *Filosofia* (Bibliographic Guide, II, 3), Milan 1943, pp. 32–34, 55–56, 125–31.

III. COMPREHENSIVE STUDIES: W. Schuppe, *Grundriss der Erkenntnislehre und Logik*, Berlin 1894; E. Domet de Vorges, *La connaissance*, Paris 1895; J. Rickaby, *First Principles of Knowledge*, Rome 1901; P. Martinetti, *Introduzione alla metafisica*, vol. I: *Teoria della conoscenza*, Turin 1904 (repr., Milan 1920); B. Varisco, *La conoscenza*, Pavia 1905; A. Riehl, *Logik und Erkenntnislehre*, Berlin 1907; J. Geyser, *Grundlagen der Logik und Erkenntnislehre*, Münster 1909; E. Dürr, *Erkenntnislehre*, Leipzig 1910; R. Jannière, *Critérium*, Paris 1912; A. Maymonce, *Analitica e critica della conoscenza*, Palermo 1913; G. Wendel, *Kritik des Erkennens*, Leipzig 1914; W. Coffey, *Epistemology or Theory of Knowledge*, London 1917; A. D’Emilia, *La teoria della conoscenza*, Spoleto 1919; id., *Coscienza e conoscenza*, Rome 1922; J. Geyser, *Grundlegung der Logik und Erkenntnislehre*, Münster 1910; id., *Erkenntnislehre*, 1912; F. Masci, *Pensiero e conoscenza*, Turin 1922; D. Mercier, *Critérium logique général*, 8th ed., Louvain 1923; F. Brentano, *Versuche über die Erkenntnis*, Leipzig 1925; D. Drake, *Mind and Its Place in Nature*, New York 1925; N. Hartmann, *Grundzüge einer Metaphysik der Erkenntnis*, 2nd ed., Berlin 1925; M. Sturzo, *Il problema della conoscenza*, Rome 1925; J. Hessen, *Erkenntnislehre*, Berlin 1926; H. Rickert, *Der Gegenstand der Erkenntnis*, 6th ed., Tübingen 1928; N. Monaco, *Critica*, 3rd ed., Rome 1928; J. De Tonquède, *La critique de la connaissance*, 2nd ed., Paris 1929; C. Nink, *Grundlegung der Erkenntnislehre*, Frankfurt am Main 1930; G. Mazzoni, *L’animo conoscente*, Padua 1931; P. Geny, *Critica*, 3rd ed., Rome 1932; M.-D. Roland-Gosselin, *Essai d’une étude critique de la connaissance*, Paris 1932; J. Donat, *Critica*, 7th ed., Innsbruck 1933; A. Naber, *Theoria cognitionis criticae*, Rome 1933; J. De Vries, *Denken und Sein*, Freiburg im Br. 1937; id., *Critica*, 1913; F. X. Maquart, *Metaphysica defensiva seu critica*, Paris 1938; C. Stumpf, *Erkenntnislehre*, 2 vols., posthumous, Leipzig 1939–40; G. Zamboni, *La persona umana*, Verona 1940; A. Brunner, *La connaissance humaine*, Paris 1943; F. Morandini, *Logica maior*, Rome 1945; A. Guzzo, *L’io e la ragione*, Brescia 1947; G. Calogero, *Logica gnoseologia ontologia*, Turin 1948; L. Veuthey, *La connaissance humaine*, Rome 1948; W. H. Werkmeister, *The Basis and Structure of Knowledge*, New York 1948.

IV. SPECIAL STUDIES: F. Salis-Sewis, Della c. sensitiva, Prato 1881; B. Spaventa, Esperienza e metafisica, Torino 1888; C. Pit, L'intellect actif, Parigi 1890; E. Domet de Vorges, La perception et la psychologie thomiste, 1918; id., Les cartes de l'expérience, 1918; E. Peillau, Théorie de concepts, 1918; id., Les images, 1919; F. De Sarlo, I dati dell'esperienza psichica, Firenze 1903; W. Freytag, Die Erkenntnis der Anwesenheit, Halle 1904; C. Guastella, Saggi sulla teoria della c., Palermo 1905; A. Farges, La crise de la certitude, Parigi 1907; P. Vallet, Les fondements de la connaissance et de la croyance, 1905; C. Stumpf, Psychologie und Erkl.lehre (Abhandlungen d. Königl. Acad. der Wissenschaften, Phil. hist. Klasse, 4), Berlin 1907; G. Canella, Il punto di partenza del problema critico-logico, Monza 1908; G. Fonsegrive, Essai sur la connaissance, Parigi 1908; A. Messer, Einführung in die Erkl.lehre, Leipzig 1909 (2nd ed., 1917); H. Gründer, De qualitatibus sensibilibus, praesertim de coloribus et sonis, Freiburg im Br. 1911; A. Tilgher, Arte, c., realtà, Torino 1911; E. V. Hartmann, Das Grundproblem der Erkl.lehre, 2nd ed., Leipzig 1914; F. De Sarlo, Il pensiero moderno, Milano-Palermo 1915; J. Volkelt, Gewissheit und Wahrheit, Munich 1918; J. Gredt, Unsere Ausswend, Innsbruck 1921; G. Zamboni, La gnoseologia dell'atto come fondamento alla filosofia dell'essere, Milano 1922; N. Abbagnano, Le sorgenti irrazionali del pensiero, Napoli 1923; E. Landmann, Die Trascendenz der Erkenntnis, Berlin 1923; G. Picard, Le problème critique fondamental, Paris 1923; J. Gredt, De cognitione sensuum externorum, Rome 1924; R. Lazzarini, Teoria della c. e dell'azione morale, Savona 1925; L. Noel, Notes d'épistémologie thomiste, Louvain 1925; H. J. Watt, The sensory basis and structure of knowledge, London 1925; J. Geyser, Auf dem Kampfefelde der Logik, Freiburg im Br. 1926; H. Maier, Wahrheit und Wirklichkeit, Tübingen 1926; J. H. Parsons, An Introduction to the theory of perception, Cambridge 1927; M. Pradines, Le problème de la sensation, I, Paris 1928; P. Wust, Dialektik des Geistes, Augsburg 1928; Y. Simon, Introduction à l'ontologie du connaître, Paris 1929; R. Duret, L'objet de la perception, 1913; L. Fuetscher, Ersten Seins-und Denkprinzipien, Innsbruck 1930; A. Masnovo, Problemi di metafisica e di criteriologia, Milano 1930; G. Söhngen, Sein und Gegenstand, Münster 1930; H. Dehove, La perception extérieure, Lille 1931; N. Hartmann, Zum Problem der Realitätsgegebenheit, Berlin 1931; G. Mazzoni, L'intelletto umano, Milano 1932; R. Jolivet, Le thomisme et la critique de la connaissance, Paris 1933; F. Olgiati and A. Carlini, Neoscolastica, Idealismo e Spiritualismo, Milano 1933; A. Carlini, Il mito del realismo, Firenze 1934; F. Olgiati, Il problema della c. nella Neoscolastica italiana, Milano 1934; J. Santelet, Intuition und Wahrheitserkenntnis, Innsbruck 1934; E. Gilson, Le réalisme thomiste et critique de la connaissance, 1913; id., Le réalisme thomiste, Paris [1936]; F. Olgiati and F. Orestano, Il realismo, Milano 1936; V. L'AIA, Il problema della fondazione della filosofia e l'oggettivismo antico, 2nd ed., Rome n.d. (1st ed., 1913); G. Zamboni, Il realismo critico della gnoseologia pura, Vicenza 1936; Various authors, Acta secundi Congressus Thomistici internationalis, Torino-Roma 1937; R. Pavese, Le premesse realistiche del problema conoscitivo, Napoli 1937; P. Picard, Réflexions sur le problème critique fondamental, Paris 1937; A. Mele, I problemi gnoseologici e metafisici, Pistoia 1938; L. Noel, Le réalisme immédiat, Louvain 1938; T. Moretti Costanzi, Pensiero ed essere, Roma 1939; F. Orestano, Nuovi principi, Milano 1939; id., Nuove vedute logiche, ibid. 1939; V. Kuiper, Lo sforzo verso la trascendenza, Roma 1940; P. Carabellese, Critica del concetto, Roma 1940; id., Da Cartesio a Rosmini, Firenze 1946; J. Miratian, Les degrés du savoir, 3rd ed., Paris 1940; B. Varisco, Il pensiero vissuto (ed. E. Castelli), Roma 1940; C. Fabro, La fenomenologia della percezione, Milano 1941; id., Percezione e pensiero, ibid. 1941; E. T. Toccafondi, La ricerca critica della realtà, Roma 1941; A. De Coninck, L'unité de la connaissance humaine et le fondement de sa valeur, 2nd ed., Louvain 1947; A. Guzzo, L'io e la ragione, Brescia 1947; Various authors, Attualità filosofiche, Padova 1947; U. Spirito, Il problematismo, Firenze 1948; J. Maquet, Sociologie de la connaissance, Louvain 1949. See also general bibliography in Ueberweg: cf. especially IV, pp. 646 ff. V. also AGNOSTICISM; CERTAINTY; CONCEPT; ERROR; EVIDENCE; JUDGMENT; IDEALISM; INTELLECT; LOGIC; PSYCHOLOGY; REALISM; SKEpticism; SENSATION; UNIVERSAL; TRUTH. Ugo Viglino