SENSAZIONE

SENSATION. - From *sensus*, *sensatio*, Greek *αἰσθήσεις*, it is the original and fundamental manifestation of psychic life, through which the first form of presence of things—the world and one’s own body—is given to the consciousness of the living being. Beyond its biological significance as a means of conservation, development, and defense of life, in man it assumes a higher value as the initial process of knowledge that provides the matter and real contents of thought (cf. *Summ. Theol.*, 2a-2ae, q. 67, a. 2, c.).

OUTLINE:

I. Sensation as a physio-psychic process

II. Classification of sensations: proper sensibles

III. Space, movement, time

IV. Sensation in the history of philosophy

V. Epistemological significance of sensation.

I. SENSATION AS A PHYSIO-PSYCHIC PROCESS

The condition of consciousness in the world is its being and manifestation in dependence on the body; the original moment in which this fundamental “situation” of consciousness is revealed is sensation, which presents itself as a fact of consciousness but with an intrinsic relation of causal derivation from a body-related fact (of the organism, and through it, of the physical universe). Sensation thus presents to inquiry a twofold direction of investigation: a) the determination of its conditioning and its physio-psychic modalities (psychophysics and experimental psychology); b) the analysis of the state of consciousness as such and of the meaning it assumes in relation to the tasks and ends of personal existence (epistemology, pedagogy, ethics, etc.). As a “conscious reaction to an organic modification,” sensation is a physio-psychic process, and indeed the moment in which, with continuity of functions, the passage between the physical and the psychic is accomplished. The elements or conditions of this process are the organ, the stimulus, and the psychic energy or potentiality of the conscious subject.

The organ is, in a certain sense, the immediate bodily subject of the faculty of sensing (*αἰσθήσεις* βέβαιον ἐν τῷ τοιαύτῃ [αἰσθήσεις] βέβαιον ἐν τῷ τοιαύτῃ [αἰσθήσεις], Aristotle, *De an.*, II, 12, 424 a 24). It is among the most differentiated structures of the living organism. It essentially consists of: a) a receptive apparatus (the peripheral nerve endings); b) the afferent nerve; c) the sensory center (a notion now considered to have not only anatomical but also physiological significance). The peripheral endings, nerve, and center constitute an anatomical-functional unity whose task is to receive the impression of the stimulus, react to it by processing it, and in this way condition the conscious response. For the different senses, there exists a constancy of nerve-central reaction expressed by J. Müller’s law (1801–58): to stimuli of different nature, a given organ always reacts according to its specific sensation.

The stimulus is an action (and consequent modification) produced on the organ. Such an action can derive: a) from external reality, specifically from modifications of bodies that act either through contact of their mass (tactile sensations of resistance, pressure, etc.), or through chemical dissociation (sensations of taste and perhaps also of smell), or through the transmission of vibratory movement (visual and auditory sensations).

b) The stimulus-action can also derive from phenomena occurring within the organ itself (e.g., processes of dissolution or degeneration of tissues; action-reaction currents between cells in the centers, from which representative states reproduce elements or complexes of external sensations). Not every activity of the physical world is capable of acting as a sensory stimulus: electricity, radioactivity, magnetism do not act as specific stimuli on human sensibility. Moreover, even the specific stimulus (tactile, visual, auditory, etc.) is not capable of exciting the organ unless it reaches and exceeds minimum and maximum limits of intensity (threshold = minimum and maximum of the stimulus). The nature of the physiological process that intervenes within the nerve endings, the afferent nerve, and even in the microstructure of the cerebral centers, seems to be electrical. It appears certain that the nerve current or wave of activity that travels along the sensory fibers is always accompanied by an electrical effect (cf. A. Edgar Douglas, *The physical background of perception*, Oxford-London 1952, Italian trans. Turin 1952, pp. 24 ff.).

Psychic energy is the potentiality, proper to the living being, of reacting with a conscious representation to the peripheral-nerve-central modification. It is from this observing potentiality—which is the first power of presence of being to itself—that sensation proceeds as knowledge. In its concluding and formal moment, sensation is therefore the actualization and perfection of the sentient as such, an activity and spontaneity, a formal and representative becoming of the subject, which has its effective causality in the depths of life as a principle of immanence and consciousness (cf. Aristotle, *De an.*, II, 5, 416 b 33; St. Thomas, *In De an.*, II, lect. 11–12, ed. Pirotta, nn. 367 ff.).

In sensation, one must distinguish quality, quantity, and tone. Quality is the representative content proper to sensation: color, sound, hot-cold, etc. (proper sensibles), movement, figure, form, size (common sensibles); cf. Aristotle, *De an.*, II, 6 and St. Thomas, *in hunc loc.*). The qualities belong to sensation not as activity, but as representation (red, cold) is not the sensing, the seeing (*αἴσθησις*), but the content or term of seeing and sensing (the sensible, *αἰσθητόν*), whether or not such a content has reality and consistency in itself independent of representation. Quantity is the degree of intensity of a sensation; and it has its reason in the essential dependence of sensation itself on the stimulus, a physical fact and therefore quantitative. The relation between quantity of stimulus and intensity of sensation has been scientifically determined in the Fechner-Weber law: the quantitative variation of the stimulus necessary to determine a variation in the intensity of sensation is a constant ratio of the initial stimulus (in weight sensations, e.g., about 1/3). This law is also expressed in the formula: to a geometric ratio of the stimulus corresponds an arithmetic ratio of the sensation. The only partial correspondence of the intensity of sensation to quantitative variations of the stimulus is related to the practical purposes of the living being; but at the same time it confirms the appropriative value of sensation, which entails a certain “reduction,” for biological ends, of the totality of the stimulus’s characteristics.

“Tone” is the affective element (of pleasure or displeasure) inherent, to varying degrees, in all sensations. Beyond these fundamental properties, every sensation, as a process in time, has a duration, and visual sensations have essential spatial extension.

II. CLASSIFICATION OF SENSATIONS: PROPER SENSIBLES. The ancient classification, proceeding from an obvious consideration that takes into account the structural difference of the peripheral organs and the qualitative difference of the objects, distinguishes five kinds of sensations: tactile, gustatory, olfactory, auditory, and visual: *“sensus esse quinque audire soleo, videndi, audienti, olfacendi, gustandi atque tangendi... Partitio ista antiquissima est et fere in contionibus celebrata”* (St. Augustine, *De quant. animae*, ch. 23, n. 41: PL 32, 1058; cf. Aristotle, *De sensu et sensato*, ch. 3 and *De an.*, II, 6, 418 a 7; Plato, *Theaet.*, 156 b). However, Aristotle already observed that *“taste contains within itself many different sensations”* (*ἡ γὰρ γεῦσις πολλὰς ἔχει διαφορὰς*, *De an.*, II, 6, 418 a 13; cf. II, 11, 422 b 17 and *Sum. Theol.*, 1a, q. 78, a. 3 ad 3).

The modern classification, based on the triple criterion of the formal difference of qualities, the anatomical-functional diversity of the organ, and the specific difference of the physical stimulus, distinguishes the following main forms of sensation: contact-pressure, temperature, weight, position, movement, pain; organic sensations; sensations of taste, smell; auditory, visual sensations.

S. of pressure-resistance. — A stimulus is a mechanical action of bodies upon particular cutaneous and subcutaneous nerve endings, which appears to produce changes in the osmotic state of the cells. The stimulus is generally qualified according to the form and physical conditions of the object (e.g., stimulus of hardness, roughness, smoothness, etc.). By virtue of the experience it provides of an obstacle and resistance to one’s own action, the stimulus of pressure-resistance contributes to establishing the conviction of the existence of the external world.

2) S. of temperature. — These correspond to specific nerve endings (Pacini’s and Meissner’s corpuscles); the stimulus consists of the molecular vibrations of the surrounding body (air) or of a tangent. Temperature stimuli are subjective in character: in a stimulus of cold, heat, etc., the objectification of the stimulus is therefore nil; where it does occur (e.g., in the stimulus of cold through contact), it is due to concomitant tactile stimuli.

3) S. of weight (baresthesia). — These are mixed stimuli of contact and pressure, but they also possess a specific element; they are generally associated with muscular and effort stimuli.

4) S. of position (baresthesia). — These stimuli report the position of the parts of one’s own body. They probably originate in the joints, but they are also influenced by the general tone of innervation and, primarily, by visual-tactile representational associations.

5) S. of movement. — Also called kinetic stimuli, these report passive and active movement (κύκλους) of one’s own body and its limbs. They are primarily of articular origin, but they also seem to arise from the changes that occur in muscles, tendons, and other dermal and endodermal tissues following motor contraction. They contribute to the clear perception of one’s own body as a source of activity, and thus to the fundamental sense of life.

6) S. of pain (acute, dull, burning, localized, continuous, etc.). — These are caused by more or less deep alterations in the tissues due to mechanical, chemical, or electrical agents. The nerve endings are specific and distinct from those responding to pressure and temperature stimuli. Pain stimuli have a more or less unpleasant affective tone (when of minimal intensity, they may descend to a neutral affective level and even be slightly pleasant); they also have a teleological significance as signals of danger and threats to the integrity of the organism and even to existence itself. Together with contact stimuli, pain stimuli are therefore among the most necessary for life («touch is the fundamental sense found in all animals... and is the most necessary of all»: Aristotle, *De an.*, II, 2, 413 b 4 ff.; cf. Thomas Aquinas, *De verit.*, q. 22, a. 5).

7) Organic stimuli. — These manifest, in a rich variety of forms, the functions and conditions—normal and pathological—of the organism (e.g., stimuli of hunger, thirst, well-being, fatigue, tension, relaxation, sexual stimuli, etc.). The organ is the diffuse nerve endings throughout the body; the stimulus consists of the physiological and microenergetic changes in organs, tissues, and cells determined by biological metabolism. While qualitatively simple from a physiological standpoint, they are complex stimuli that are difficult to analyze: pressure, contact, temperature, and muscular stimuli all play a part in them; yet their affective tone is specific and original. They condition the «behavior» of the soul and, in man, even, in part, higher affective states. Together with pain stimuli, they serve as the phenomenological basis for the concepts of happiness, good, evil, etc.

8) With the name of **censesthesia** (ζουντή, αισθητήσις, common sensation), modern psychology designates the immediate awareness (which may also be understood as the basic and undifferentiated form of organic stimuli) that the soul has of its own body and its general state: a vague and somewhat obscure sensation, which may be described as a diffuse internal tactile sensation with a slightly but positively pleasant tone. Through it, the subject or biological ego has its first and concrete presence to itself, which the other specific stimuli have the task of intensifying and differentiating; censesthesia is therefore posited as the experiential foundation of the very concepts of existence and life.

9) S. of taste. — The organ consists of particular nerve endings on the tongue (fungiform papillae) and palate; the stimulus consists of chemically dissolved bodily substances. Already St. Thomas noted the affinity of taste with smell: *«Odor enim est sapor quandam affinitatem habent»* (*In De sensu et sensato*, lect. 2, n. 23; cf. lect. 9, n. 118: *«utrumque eorum est fere eadem passio»*). Taste stimuli are subjective affections: they therefore present no «external» objectification nor spatial determination.

10) Olfactory stimuli. — The organ consists of the nerve endings of the olfactory membrane; the stimulus consists of particles of bodies in a gross state, introduced through respiration. In some animal species (e.g., bees), olfactory stimuli have a preeminent significance over all others. In man, they are secondary (*«sensum olfactus peiorem habemus et per comparationem ad cetera animalia et per comparationem ad ceteros sensus qui in nobis sunt»*: St. Thomas, *ibid.*, lect. 9, n. 119). According to Pradines, taste and smell are «senses of need» in that *«nous font connatire les choses comme répondant à nos besoins»* and thus to the impulses that periodically drive us toward the search for and appropriation of external conditions necessary for the preservation and perpetuation of our existence (*Traité de psychol.*, 3rd ed., Paris 1948, p. 498). Yet this teleology must be admitted to be common, though with different expressions, to all stimuli (cf. St. Thomas, *In De sensu et sensato*, lect. 2, n. 24).

11) Auditory stimuli. — These arise from the excitations that the vibrations of bodies, transmitted through air or another elastic medium, produce on the nerve endings (Corti’s fibers) of the cochlear nerve. Homogeneous, regular vibrations produce «sounds» that are clear and distinct; irregular, mixed vibrations produce «noises» and «clangs». Auditory stimuli have a particularly synthetic character: elementary sounds (e.g., of the sea, wind) can merge into a single vast auditory sensation. In relation to time, individual sounds, through a certain «auditory memory,» persist as stimuli beyond their physical reality—a fact of extreme importance for language (v.), which would be impossible if phonetic elements (syllables and words) did not continue in the representative unity of the phrase and the period. Moreover, measure, rhythm, and proportion have given auditory stimuli particular aesthetic value (music).

12) Visual stimuli. — These are determined by luminous vibrations that excite, probably through an electro-vibratory effect, the nerve endings (cones and rods) of the retina. Individual wavelengths produce «elementary colors»; the ensemble of wavelengths of the spectrum produces «white, light»; «black,» which psychically has a positive value like every other chromatic sensation (the stimulus is either the very limit of a chromatic sensation or an internal excitation of the nerve), physically corresponds only to the absence of vibrations. Particularly in visual stimuli, the following phenomena must be noted:
a) Fusion phenomena: vibratory stimuli corresponding to different colors, if they simultaneously excite the retina, determine a psychically simple response.
b) Contrast phenomena: visual stimuli close in space or time influence and modify one another.
c) Afterimages: an intense visual stimulus persists after the physical stimulus has ceased (this phenomenon, to varying degrees, is general for all stimuli and is related to the persistence of nervous excitation).
d) Binocular vision with the effect of a single image was already noted by St. Thomas (*In De sensu et sensato*, lect. 19, n. 284) as due to the central unity of the organ.
e) All visual stimuli are spatial. Owing to their immense synthetic capacity (the visual angle can encompass an infinity of objects), visual stimuli play a principal role, in the sighted, in the manifestation of the external world.

With their clear representation of distance (v. below), they are in a certain way like an amplification in space of the tactile perceptual sphere. Thus, from an objective standpoint, they constitute the highest perfection of sensibility, and visual terms and images have been adopted to denote the very activity and values of thought (vision, idea, evidence, intuition, etc.).

Individual external senses, by reason of their objective-functional discrimination, would not enable the subject to form that organic and unitary representation of objects which is necessary for effective biological behavior in the physical environment of existence. External senses therefore extend into internal sensibility, which has the function of unifying, representing, recalling with reference to time, and evaluating the contents of external senses (common sense, imagination, memory, reminiscence, estimative power, cogitative power; V. these entries, and cf. the clear exposition in Sum. Theol., 1 p., q. 78, a. 4).

III. Space, Movement, Time

Space (figure, size, form) and movement (rest) which Aristotelian-Thomistic psychology qualifies as “common sensibles,” since they are the objects of more than one sense, constitute a further plane of objective determinations of sensibility.

1. Space

Empirical theories (Berkeley, Spencer, Taine, Lotze, Wundt) regard space as a “secondary” datum, i.e., derived from a constructive process of perception; nativistic theories (Aristotle, St. Thomas, much of modern psychology) affirm, within certain limits, the “original” (native) character of spatial representation. Nativism must not be confused with “apriorism” (Kant), which intends space as a subjective form a priori conditioning experience. It seems difficult to deny the original character of spatial representation. Even the empiricist explanation that derives space from the constructive movement of the organ does not in reality oppose nativism, inasmuch as the movement of the eye along the points limiting the object presupposes an extension that determines, as figure or form, but does not create as pure extension (furthermore, the copious researches of Gestalt- and Ganzheitpsychologie have shown that even formal structures in many cases are given as global and unitary stimuli, so that the visual apprehension of “form” often has an original character). The physiological antecedent of visual spatial sensibility is the spatially configured extended excitation of the stimulus on the retina. That the extended discontinuous, as material reality perhaps is, is represented by consciousness as continuous is in accord with the law of “threshold” (already known and discussed by Aristotle and St. Thomas: cf. De s. et de s., cap. 6), whereby stimuli whose spatial distance is below the minimum discernible by the physiopsychic structure of the sense act as a single stimulus and thus cause a continuous visual representation (the continuous, therefore, as given in macroscopic experience, may be referred to the synthetic function of sensibility). The constructive activity of visual sensibility is most fully expressed in the perception of the third dimension. Distance and depth do not seem to be objects of elementary sensibility (a luminous point in darkness, without reference points, cannot be evaluated as to its distance), but are rather due to a perceptual elaboration (in which there participate: binocular parallax; the different variation of the visual angle for near and far objects when the eye moves in their direction; the reference of the apparent size of an object to its known real size; the movement necessary to approach the object, etc.). Tactile spatial sensibility seems essentially of a genetic-motor nature. Pure contact sensibility, not integrated by visual-tactile representations (imagination and memory generally intervene in the spatial construction of objects), does not give, at least in distinct form, the third dimension and the form of objects: both are “constructed” through the representation occasioned by the tactile organ (hand) traversing the surface delimiting the object; such, as is well known, is spatial representation in the blind.

2. Movement

Movement, as change of position of external objects in space, is a modality of visual-tactile stimulus and thus an original datum of sensibility. But since, as pure variation of position, motion is relative and reversible, the original visual sensibility by itself does not refer to the real movement of an object. Even in movement sensibility a process of physio-psychic construction may intervene: an immobile stimulus acting on the retina from two nearby positions succeeding one another within an interval of time less than the differential threshold is seen not as two images but as one, moving from the first to the second position (cinematograph and stroboscopic apparent movement); in this case movement is a pure perceptual datum. Tactile sensibility of movement is mainly active, i.e., dependent on the real movement of the organ (hand) over the object. More obscure—unless the habitual integration of internal representative sensibility intervenes—is tactile sensibility of passive movement (of the object over the organ).

3. Time

Phenomenologically, time is the duration of a phenomenon (object, sensibility, datum, representation). The “before” and “after,” the “beginning,” the “duration,” the “ending” are essential modalities of experience, and therefore, concretely, time is given with experience itself: tempus non sentitur quasi aliqua res permanens proposita sensui, sicut videtur color, magnitudo, sed propter hoc sentitur quod sentitur aliquid quod est in tempore (St. Thomas, In De s. et de s., lect. 18, n. 27). In the concrete content of perception, through an abstractive intuition of spiritual consciousness, the real character of “duration” and “succession” is grasped, and these thus come to be universal representations. In its formal aspect, time is therefore not an object of sensibility, yet as real duration it is an objective character of all sensibility. Kant’s doctrine of time and space as a priori forms of sensibility is therefore inexact. Time and space, as concrete contents or values, belong to the objects of real experience (time moreover to experience itself as successive psychic becoming in consciousness). The a priori of sensibility in relation to space and time is not a thetic function but merely a constructive and organizational one; and what is transcendental for sense must be understood as the perceptual-elaborative relation of physiopsychic structures to real stimulus.

IV. SENSATION IN THE HISTORY OF PHILOSOPHY

The problem of sensation, its value and significance, is fundamental in almost all philosophical thought. The Presocratics inclined toward sense (v.)—that is, toward the ultimate reduction of all knowledge to sensation—understanding sensation, for the most part, in a passive and materialistic sense. For Empedocles, sensible qualities are physical emanations of things: “color is an effluence of a river, proportionate to the eye and perceptible” (Men., 76, d.; cf. Aristot., De sensu et sensibilibus, 2, 438 a 4, and De anima, 1, 2). Similarly, in Democritus (v.), sensing is the passive reception of corporeal images (the “εἰδώλια” that enter the organ: cf. Diog. Laert., IX, 44). But already in Protagoras, sensation is understood in an active sense: color, heat, hardness, etc., “are nothing in themselves” (καθ' αὐτὸν μὲν οὐδέν) but arise from a mutual agreement (of object and sense) and universality, while from movement (Theaet., 157 a ff.; cf. 154 a 156 b ff.).

In Plato, sensation is an affection of the body that presents itself to the soul and thus becomes in the soul a principle of recollection (v.): “The being (affections of the body) hides from the soul what is called insensibility...; but when body and soul together undergo the same affection (ἐν ἑνὶ πᾶσι) and are not separated, this you may not improperly call sensation” (Phil., 33 e–34 a; cf. 39 a).

In Aristotle, the problem of sensation is developed with rich analyses and observations. He surpasses the materialistic naturalism of the Presocratics with the concept of sensation as “a reaction to forms or sensible images without matter” (De anima, II, 12, 424 a 18), a formula that seems to correspond to the expression of medieval terminology: “recipere intentionaliter, obiective.” For Aristotle, sensation is, in some measure, knowledge: ἡ δ' αἴσθησις γνῶσίς τις τῷ ἐξ ἀνθρώπων (De generatione animalium, I, 23, 731 a 43); if it must be called alteration, “since it is manifest that sensation occurs through the body” (De sensu et sensibilibus, 1, 436 b 6), it is nonetheless a special kind of alteration—“ἀλλοίωσίς τις ἑτερογενής” (De anima, II, 5, 416 b 34; 417 b 7)—and while it involves a passive moment (πάθησις, κινεῖσθαι: ibid., 416 b 34), it is formally an immanent and perfective act of sensing (εἰς αὐτὸ ἐπιστροφή τις καὶ εἰς ἐντελέχεια: ibid., 417 b 6).

As for its biological significance, sensation is ordered to the preservation and defense of the animal (σωτηρίας ἕνεκα: De sensu et sensibilibus, 1, 436 b 20), but in man, sensitive knowledge is the objective condition of thought: “the intellect does not know external things unless through sensation” (ibid., 6, 445 b 16–17; cf. De anima, III, 8, 432 a 8: a fundamental anti-Platonic motif in Aristotelian epistemology).

Stoicism, and even more Epicureanism, reduce all spiritual activity to sensation and thus posit sensation itself as the norm and criterion of truth (cf. Diog. Laert., VIII, 4 ff., and X, 31: “Epicurus sets up as the criterion of truth sensation, preconceptions, and affections”).

Plotinus reaffirms sensation as an internal activity of the soul: “we understand sensation not as something we undergo (πάθησις) but as an activity concerning sensible impressions and as judgment” (Enn., III, 6, 1, 26).

St. Augustine, following Plato, defines sensation as “a passion of the body not hidden from the soul itself” (De quantitate animae, cap. 25, n. 48: PL 32, 1063; cf. cap. 23, n. 41; cap. 30, n. 58), that is, an affection of the body that is immediately present to consciousness: “The soul intends itself in touch, and by it feels and discerns hot, cold, rough, smooth, hard, soft, light, heavy” (ibid., cap. 33, n. 71: PL 32, 1074. Cf. De Genesi ad litteram, XII, 24: PL 34, 475, where Augustine seems to attribute sensation solely to the soul: “For it is not the body that senses, but the soul through the body, which it uses as a messenger to form within itself what is announced from without”; cf. Summa Theologiae, 1a, q. 84, a. 6). The statement “aliud est sentire, aliud cognoscere” (De quantitate animae, cap. 24, n. 45: PL 32, 1060) does not mean, in context, that sensation is not knowledge, but rather that there is a knowledge that is not sensation: sensation is in itself true, insofar as it apprehends reality, but it does not possess that science “which they wish to be understood as remaining remote from the senses and living in the mind” (Contra Academicos, III, cap. 11, n. 26; cf. De vera religione, chaps. 33 and 36).

The doctrine of St. Thomas on sensation is a deepening of Aristotelianism. Sensation is the first degree of knowledge, intrinsically conditioned by the corporeal organ: “the soul senses nothing without the body, because the act of sensing cannot proceed from the soul except through a corporeal organ.” As an act of a corporeal organ, the sense is a passive power: “which is by nature mutable by an external sensible” (Summa Theologiae, 1a, q. 78, a. 3 c.): a mutation not only material-physical but also spiritual-intentional: “for the operation of the sense, a spiritual mutation is required, by which the intention of the sensible form is made in the sensory organ” (ibid.; cf. In De anima, II, lect. 2a, ed. Pirotta, n. 553). This “intentional” mutation (the “species impressa” of traditional terminology) is the stimulus itself insofar as it is an objective determination and formal principle of representation (cf. In De anima, loc. cit., where St. Thomas develops Aristotle’s concept of sensation as “receptio formae sine materia”).

Sensation is not, however, a purely passive moment: “to sense, insofar as it concerns the reception of the sensible species, is called passion; but insofar as it concerns the act that follows upon sensation itself, perfected by the species, it is called operation” (In I Sent., dist. 40, q. 1, a. 1).

The term of sensitive representation can only be a “form” embodied in time and space: “the object of any sensitive power is the form insofar as it exists in corporeal matter” (Summa Theologiae, 1a, q. 85, a. 1, c.; cf. ibid., q. 75, a. 6, c.); “the sense knows being only under ‘here and now’” (ibid., 1a–2ae, q. 15, a. 1). Therefore, neither the universal nor truth in the formal sense is to be sought in sensation (ibid., 1a, q. 17, a. 2, c.; cf. De veritate, q. 1, a. 11, c.). Nonetheless, the value of sensation for human knowledge is fundamental, since through it the presence of reality to consciousness is realized, and in sensory representations—especially in internal sensation—the highest richness and objective consistency is attained.

In the cogitative faculty—the intellect finds the concrete content for the intuition and abstraction of universal values (cf. especially, on this fundamental point of Thomist epistemology, *Sum. Theol.*, 1ª, q. 84, a. 6-7, q. 85, a. 1; V. CONOSCENZA; INDUZIONE). In the Renaissance, sensation (*sensazione*) is particularly CAMPANELLO (v.).

Sensation (which is not a mere “passion” but a judging act: *Metaph.*, I, Paris 1638, p. 42) is concrete and immediate knowledge, and thus the foundation of true philosophizing: “sentire est praesentis obiecti notitia” (Theol., X, cap. 3, a. 5); “duo sensu philosophandum esse existimamus. Eius enim cognitio omnium certissima est, quia fit obiecto praesente” (*Prodromus*, François 1617, p. 27).

In modern philosophy, Descartes, having reduced the essence of the subject to a pure “thinking thing” (*Med.*, VI), understands sensation as “the passive faculty of... receiving and recognizing sensible ideas” (ibid.). Organic sensations “ne sont autre chose que de certaines façons confuses de penser,” dependent on the “mixed” union of “spirit with body,” and to the sensations of the external world there correspond in bodies certain properties, even if dissimilar to the sensations themselves (ibid.; cf. *Passiones an.*, I, 23, and *Princ. philos.*, IV, 189).

For Spinoza, “the ideas we have of external bodies indicate rather the constitution of our own body than the nature of the external bodies” (*Eth.*, II, prop. 16, coroll. 2). According to Malebranche, sensation is “une modification de notre âme par rapport à ce qui se passe dans le corps auquel elle est unie.” Sensations therefore “ne sont que dans l’âme” (*De la recherche de la vérité*, I, cap. 13, § 1-2).

In empiricism (v.), sensation is the primary source of knowledge, and its contents attain the principal value of reality. For Locke, “the first capacity of the human understanding consists in this, that the soul is apt to receive the impressions that are made upon it either by external objects through the senses or by its own operations... On this foundation all notions are established” (*Essay*, II, cap. 1, § 24). Berkeley, denying the existence of matter as a thing in itself, understands sensations as representations or “ideas” produced in our spirit by God Himself. Material things resolve into sensations: “light and colour, heat and cold, extension and figure, in a word the things we see and feel, are nothing but so many sensations, notions, ideas, or impressions on the senses” (*Principles*, § 5). For Hume, sensations are the original perceptions of the mind, namely impressions (*Treatise*, I, part 1, sect. 1, § 1). Sensations, together with the “ideas” that are their residue in the mind, are ultimately the only things of which we have absolute certainty (“nothing is really present to the mind but its own perceptions”: ibid., part 4, sect. 2, § 5). The senses “do not present their impressions as images of something distinct or independent or external” (ibid., § 3), and “it will always be impossible to decide with certainty whether [the impressions] proceed immediately from the object or are produced by the creative power of the mind, or are received from the Author of our being” (ibid., part 3, sect. 5, § 1).

In Kantian criticism, sensibility is “the capacity to receive representations insofar as we are affected by objects,” and sensation is “the action of an object on the faculty of representation insofar as we are thereby affected” (*Kritik d. r. Vernunft*, I, part 1, § 1). The representation of what is given in sensation is called by Kant an “empirical intuition”: it presupposes a formal element (space, which is a priori in the mind); for outer sense, space; for inner sense (and for all sensations insofar as subjective experience), time. Space and time are therefore “pure” intuitions, transcendental conditions for the possibility of the representation of objects in sensation (ibid., § 2 ff.). With Kant’s doctrine, the creative activity of the subject in relation to reality as object of our experience (phenomenon) is affirmed.

In Hegelian idealism, sensation (*sensazione*) denotes the first determination of spirit, still immediate and undeveloped in the antithesis of an objective against the subject. It is “the form of the dull agitation of spirit in its individuality devoid of consciousness and intellect” (*Encycl.*, § 400). Everything that takes place in spiritual consciousness and reason—Hegel affirms—has in a certain way “its source and origin in sensation,” but only in the sense that sensation is the first and most immediate manner in which the contents of spirit appear. For sensation, the ego of consciousness (which belongs to being-for-self) is determined as spiritual corporeality; hence sensation is “the healthy coexistence of individual spirit in its corporeality” (ibid., § 401). Absolute interiority and immanence of all determinations given through sensation: “Sensations are... modifications in the substantiality of the soul, posited in its being-for-self, which is identical with substantiality” (ibid., § 402).

ROSMINIANI (v.) distinguishes two modes of sensitive perception: a) there is the “fundamental feeling” and universal “by which we feel life to be in us” (*Nuovo saggio*, sect. 2, part 3, cap. 1, a. 1): this is a permanent activity and a “vigilant and actualized sensing of the state, whatever it may be, of our sensitive body” (ibid., a. 3), arising immediately “from the first individual union of spirit with an animal body” (ibid.). The various sensations by which we subjectively feel our body and its parts are modifications of the fundamental feeling. The sentient soul, present throughout the body, also perceives the changes produced “in the sensitive parts by the force of an external body”: “the perception of this passivity that the sensitive soul experiences in a given way determined by the quality of the sensation is the sensitive perception of bodies” (ibid., a. 4).

Sensation has an immanentist meaning in the actualism (v.) GENTILI (v.). It is the initial and obscure moment from which the ego begins the process toward its full spiritual reality as the unity of subject and object, i.e., as thought and self-consciousness: “Pure sensation, feeling, is therefore the principle in which thought, at its first dawn, and reality, in its deepest root, coincide” (*Introd. alla filos.*, cap. 4, n. 20, Milan-Rome 1923, p. 87). “That ground, dark in itself but which [the ego] illuminates by its eternal becoming, that first point from which it sets out on its eternal path, the solid and unshakable base on which it builds itself and, within itself, all that determined world which it progressively determines within itself—that is sensation, which, viewed from without, is the body, the very physical world” (ibid., cap. 5, n. 20, pp. 107–108).

SIGNIFICATO GNOSEOLOGICO DELLA S.

The idealistic conception, which understands sensation (*sensazione*, s.) as the first form of the immanent spontaneity of the spirit, grasps one of the authentic meanings of feeling, namely its character as an activity and subjective transcendability. Sensation, by which the first forms of consciousness in act are posited, is lost in its essential nature if it is reduced to mere passivity, with the same meaning as the action-reactions of the physical world. Against the materialistic reduction of feeling to a mere cosmic process (not overcome by the so-called "psycho-physical parallelism" of Wundt and others, which makes the fact of consciousness a simple "epiphenomenon" [v.] of the physiological fact), the interpretation of sensation as a moment of spiritual subjectivity is correct. In reality, the gradual determinations that sensation assumes in the unfolding and affirmation of life in the world (from the most obscure "protopathic" sensibility of unicellular animals, which is barely a glimmer of "presence" and "awareness," to the complex critical differentiations it assumes at the summit of its perfection in man) have their first source in the transcendability of the sentient subject, which unfolds in multiple "forms" in living beings and, in man, is posited as a spiritual principle, an ontological synthesis of feeling and thinking, of experience and self-consciousness. In this way, sensation is the immediate manifestation of the presence of the sentient principle in a body individuated in time and space, and it is determined in particular forms according to the structures of the sensory organs and the action of the physical world upon them.

Consequently, while sensation is posited as an immanent form of being of consciousness, it is also, in various ways according to the increasing degree of its qualitative differentiation, a revelation of the world in the objective relations that the world itself assumes with the subject. Sensation—as every intentional form of consciousness—is therefore neither pure subjectivity nor pure objectivity: on the contrary, it expresses (and in this direction the interpretations of empiricism and perceptualism [v.] seem to be reconciled) the determination of the physical world into "qualities" and "modes of representation" that have their formal principle in the expressive potentiality of the sentient principle, but are objectively conditioned—in their spatio-temporal significance as "objects" and "things"—by the reality that becomes the physical stimulus of the organ. This accounts, on the one hand, for the relative characters of sensation (dependent primarily on the "fluidity" of the conditions of the sensory organs, already clearly noted by Greek thought: cf. the "ten tropes" of Aenesidemus in Sextus Empiricus, *Pyrrh. hypoth.*, I, § 14 ff.; V. SKEPTICISM), and on the other, for the insurmountable conviction of objective reality and "transcendence" with which sensation is posited in human spiritual consciousness.

If we wish, therefore, to clarify the gnoseological meaning of sensation, the following conclusions seem acceptable:

a) Pure sensation, while positing itself as a form of cognitive presence, is an initial and obscure form of knowledge that does not realize a full opposition between object and subject, ego and non-ego.

b) The world of sensation does not, as phenomenism (v.) claims, entirely and without ontological residue resolve the world of reality; nor is it a mere reflection of a superior ideal reality (Plato). Not all aspects of the real are given in sensation, which is only a partial representation of the world in some of its dynamic physical characters. The realistic meaning of sensation lies in its value as a transcription in terms of consciousness of real phenomena and activities of matter, and in its conditioning and proportioning to them.

c) As the first contact of consciousness with reality, sensations are moments in which being is given, albeit in an inappreciable way (not as being in itself, but in its concrete manifestations and physical activities). From this obscure givenness of being in sensation, the intelligence can proceed to the determination of the ontological ground on which the sensible object emerges and consists: moving in this direction, it seeks the principles and causes of corporeal being (metaphysics). From sensation, moreover, the intellect proceeds to the determination of sensible objects and of sensations themselves in their meaning for the sentient subject: in this other direction, sensations reveal their biological, existential, aesthetic, social, and moral character (an ethical system such as hedonism resolves moral values—good and evil—into the affective tone of sensations—pleasure and pain), and thus also their essential function for man, a spirit incarnate in a sensible body, in relation to the attainment of particular ends and the ultimate end of existence.

d) Pure sensation as such, having no conceptual value, also has no meaning of "certainty" in the gnoseological sense of the term. Sensation is not evident in that pure sensation is a being of existence, but an awareness of "modes," "affections," "qualities." However, in man, by virtue of the unity of the sentient and intelligent principle (sensation in man is almost never presented in a "pure" state), with sensation there is given, in judging consciousness, the presence of the concrete existing entity (in certain modes and forms of its spatio-temporal activity). The objects of sensation therefore possess a value of existence, but one that has different degrees: 1) There is a value of phenomenal-representative reality: this is proper to every object of sensation, but only insofar as it is "given," "represented"—a weak, first-degree reality that belongs also to dreams, illusions, hallucinations, and all the "false" representations of the senses. 2) A value of subjective-psychic reality: this is proper to every sensation insofar as it is a psychic fact of the subject—an ontological but "subjective" and "accidental" reality. 3) A value of transgressive, transcendent reality, according to which the object of sensation reveals itself as having an existence of its own in the physical world. Such reality, taken as a whole, is the intentional reference of all sensibility: through it, the real "situation" of the sentient being (animal-man) in the world is explained and clarified; its existence with multiple relations of biological needs, necessities, and dependence on physical reality.

But in relation to individual objects of sensation, transcendent reality (and its degree) are not universally determined and must be established by the criterion of the "critical convergence" of the various sensory planes, and also by the more or less positive and effective function that an object of sensation fulfills in relation to the existential needs of the living being.

e) In pure sensation, as there is no formal evidence, so there is no formal truth or error: sensation is always determined by the encounter of an objective stimulus (external or internal) with the subjective conditions of the sense, and as such it is neither true nor false. But, by reason of the contingency of the conditions of the object and the subject, the sensory representation may, to a greater or lesser extent, fail to correspond to the conditions of reality in itself (limit cases are hallucinations and, in general, representations arising from pathological affections of the organ): *"Sensum affici est ipsum sentire. Unde per hoc quod sensus ita nuntiant sicut afficiuntur, sequitur quod non decipiamur in iudicio quo iudicamus nos sentire aliquid. Sed ex hoc quod sensus aliter afficitur quam res sit, sequitur quod nobis nuntient aliquid quod rem aliter quam sit"* (Sum. Theol., 1a, q. 17, a. 2, c.). This intrinsic condition of sensibility does not entail a negative judgment on its value and positivity. For, as St. Thomas still affirms, *"natura... sensibilium qualitatum intelligere non est sensus sed intellectus"* (ibid., 1a, q. 78, a. 3, c.), it is for thought—in which sensation is ultimately clarified and defined as knowledge—to determine the positive meaning and the limits of sensation as a revelation of being.

The text, or the thing expressed in the phrase in the symbolic-real plane. The study of the biblical senses is the object of that part of biblical interpretation (v.) known as noematics (from vóhma, “thought”).

SUMMARY:

I. Classification

II. Literal Sense

III. Typical Sense.

I. CLASSIFICATION

After many centuries of proposals and discussions, the distinction of the biblical senses is not unanimous. One of the most obscure questions currently under discussion is that of the classification of the biblical senses (J. Daniélou, Les divers sens de l'Ecriture dans la Tradition chrétienne primitive, in Ephemerides theologica Louvainenses, 24 [1948], p. 119). All deplore a confusion of terms, the manifold misunderstandings, and the heated polemics concerning the “senses” of Holy Scripture. Scholars of every age, not excluding modern ones, often fail to understand one another and consequently engage in conflict precisely because of the use of terms, some of which have a long and intricate history, as happens today, for example, in certain mariological questions (Gen 3:15 and Rev 12:1-18). More often than not, it is a matter of words. An abundance of such technical expressions, philosophical-scholastic subdivisions coined here and there, would have to characterize all the nuances of meaning of individual biblical texts and of the various biblical senses. Thus the terms: literal and real, historical and spiritual, mystical, typical; dogmatic (allegorical, messianic), moral (tropological), anagogical (eschatological); proper and improper (tropical, metaphorical); figurative and figurative; explicit and implicit; philological, logical, theological; consequent, full, eminent, accommodative, etc. Today there is agreement that this terminology must be urgently reduced to avoid misunderstandings: a simplification based on the essence of “sense” rather than on secondary or accidental points of view. Once an improper terminology that generates confusion is eliminated, “let us accustom ourselves to calling things by their proper names and we will always be easily understood” (G. M. Perrella, Introduzione generale [see bibliography], p. 253, note). First of all, when it comes to interpreting the hermeneutical terms of the ancients (St. Paul, the Fathers, the Scholastics), e.g., “spiritual, allegorical, typical,” one must never suppose forthwith the meaning that is attributed to them today. Finally, it goes without saying that biblical hermeneutics, and noematics in particular, also requires clear concepts regarding biblical Inspiration, its nature, and its extent.

The above definition of the biblical senses already hints at their twofold kind, literal and real, since the concept of the mind can be manifested only in the word or in the res (thing, action, fact, person, institution), and can be expressed either immediately or mediately. The first, the literal or verbal, grammatical, historical sense (common to all human books) necessarily exists also in the books of the Bible, which are due to human authors, true authors although merely instrumental. Instead, the real “typical” sense is an exclusive prerogative of Holy Scripture, intimately connected with the prerogative of Inspiration, a sense understood only by the principal author, God, and knowable to men only through Revelation.

“In no science invented by human industry can, strictly speaking, be found anything other than the literal sense; but only in this Scripture, whose author is the Holy Spirit, while man is merely an instrument, is the spiritual sense found” (St. Thomas Aquinas, Quodlibet 7, q. 6, a. 16); “Whereas in all sciences words signify, this science (Sacred Scripture) has the peculiar property that the things signified by the words themselves also signify something” (id., Summa Theologiae, I, q. 1, a. 10).

An immediate consequence of this unique character of the Book of Books is the two methods, complementary to each other, for discovering the scriptural sense: literary heuristics and authentic heuristics, i.e., the rules of biblical interpretation that are common or rational and those that are proper or Catholic.

II. LITERAL SENSE

Pope Pius XII points out to the Catholic exegete “among all his tasks the highest one, namely, to find and expound the genuine thought of the Sacred Books... Therefore they must with all diligence trace the literal meaning of the words...” (encyclical Divino afflante Spiritu, in AAS, 35 [1943], p. 338). The most interesting and most debated problems concerning the literal sense are three: 1) its subspecies, so to speak, especially the full, consequent, and accommodative senses; 2) its universality: every biblical statement contains a literal sense; 3) its uniqueness: no statement of Holy Scripture contains two or more disparate literal senses.

4. Subspecies of the literal sense

Words can be taken either “secundum proprietatem locutionis” (St. Thomas Aquinas, Expositio in Epistolam ad Galatas, 4, lectio 7), in their proper, obvious, native sense, or “secundum similitudinem seu metaphoram” (ibid.), in their improper, metaphorical, transferred, figurative sense (e.g., Christ is compared to a lion, to a lamb, to a vine).

The consequent sense is important in theology and useful for Christian life if it is employed with due moderation and caution.

Treating of the literal scriptural sense, by way of an appendix one may also speak of the "accommodated" or "accommodative" sense, inasmuch as, by some verbal or real resemblance, words of the Sacred Books are adapted to persons or things entirely different from those intended by the human-divine author. Such accommodation, especially that by extension, as is often found in liturgy (others think it should rather be treated as the fuller sense), is lawful and useful, "provided it is done with modest reason and sobriety; but one must never forget that such use of the words of Holy Scripture is almost extrinsic and adventitious to it, and that above all in our own day it is not without danger..." (Pius XII, *Divino afflante Spiritu*, loc. cit., p. 339). If, however, that resemblance is found only in the words, such accommodation by allusion is rather abusive and a reprehensible play on words.

5. Universality of the literal sense

A fundamental principle of all sound biblical exegesis is that there is no text of Holy Scripture that does not have a literal sense, whether proper or improper. Whoever abandons, at least in practice, this norm, devaluing the literal sense, builds on sand and easily succumbs to subjectivism, pietism, or pneumaticism: "In this way he rejects the golden rule of the Church’s doctors, so clearly formulated by the Angelic Doctor: 'All senses are founded upon one, namely the literal, from which alone an argument can be drawn'; a rule which the Supreme Pontiffs sanctioned and consecrated when they prescribed that, above all, the literal sense be sought with every care..." (Letter of the Pontifical Biblical Commission to the Italian episcopate, *AAS*, 33 [1941], p. 467). "Thus, with the new exegesis, called symbolic and spiritual — they affirm according to their false opinions — all the difficulties vanish which only those encounter who adhere (as regards the Old Testament) to the literal sense of Scripture" (Pius XII, encyclical *Humani generis*, in *AAS*, 42 [1950], p. 500; *Civ. Catt.*, 1950, III, p. 465).

---

Sensory stimuli; in this latter sense one speaks of visual, auditory, tactile, etc., sensation to indicate the capacity of a sensory stimulus, quantitatively variable, to reach the threshold of consciousness, a capacity that can be precisely measured.

It may be said, for example, that the maximum limit of man’s auditory sensation, i.e., the capacity to perceive acoustic sensation from sound vibrations, is lower than that of the dog, because man no longer perceives as acoustic sensation vibrations exceeding 20,000 per second, while the dog can still perceive acoustically vibrations reaching frequencies of 38,000.

Upon this concept of sensation one of the most interesting and fruitful chapters of psychophysiology has been constructed. It should be remembered that sensation, so understood, must be distinguished from excitability, which is proper to living beings in general, including unicellular organisms, and constitutes a vast and complex chapter of general biology.

One can speak of sensation only where there exist differentiated nervous structures that specifically underlie this function; the more integrated and differentiated the anatomical structures, the more varied and complex the forms of sensation.

From a neurobiological and clinical standpoint, sensation is generally distinguished into protopathic (Head) and epicritic, according to the greater or lesser intellectual content of the various forms of sensation. These concepts are biologically very important, linking up with the meaning of "consciousness" as "vigilance" (v. SENSATION).

The disturbances of sensation, which are of great importance from the standpoint of neurological semiotics, concern the subjective and objective forms of sensation. Subjective forms include paresthesias (tingling, numbness, tickling, sensation of "dead flesh," etc.), causalgia (burning pains produced by irritation of the sympathetic nerve network enveloping the nerve and its satellite blood vessels), and pains (e.g., neuralgias). Objective forms include disturbances of tactile, painful, thermal sensation, of tactile localization, of tactile discrimination, of pressure or weight sensation (baresthesia), of painful sensation from excessive pressure, of vibratory sensation (pallesthesia), of pressure localization, of recognition of the position of the different segments of a limb, of a limb as a whole, and of passive movements (bathyesthesia, arthrokinetic sensation). Generally considered separately are disturbances of stereognosis, i.e., the ability to recognize the shape, consistency, and volume of an object; this is in fact a synthetic process of the various forms of elementary sensation.

In clinical practice, as a result of the organization into anatomo-topographical structures of the various sensory pathways, so-called dissociations of sensation are observed: of the peripheral type (deep sensations are preserved and superficial ones abolished); of the tabetic type (thermodolorific, baresthetic, and superficial tactile sensations intact, while pallesthesia, bathyesthesia, and tactile discrimination are abolished); of the syringomyelic type (roughly the opposite picture of the preceding form).

The sensory pathways reach the optic thalamus (posterior part of the external nucleus), from which sensory tracts proceed to the cerebral cortex. The function of the thalamus is considered important: it seems, in fact, that it is responsible for the elaboration of the emotional, affective aspect of every form of sensation, leaving to the cortex the more delicate task of discriminating, identifying, and evaluating the various stimuli. It is evident that there cannot be an equal behavior in this regard for all forms of sensation; painful impulses, which are those most charged with emotional content, are largely elaborated intrathalamically; for touch, however, the emotional content is much less, and thus the thalamocortical pathway is much richer. It seems that this anatomo-functional organization is the true basis of protopathic and epicritic sensation, and on this basis the protopathic aspect of sensation shows intimate traits of union with the so-called cenesthesia (v.). Thalamic lesions can cause very intense, paroxysmal, persistent, intolerable pains, unaffected by any therapeutic means; these may perhaps be considered as symptoms of "release" of thalamic activity from the inhibitory influence of the cortex.

From what has been said, it can be understood how profound alterations of the various sensations may exist without the psychic state thereby suffering in its integrity, and, conversely, profound psychic alterations may exist without any compromise, or only a very slight one, of sensation.