CAUSE. — I. Concept.
According to the most reliable etymology, the first scientific application of the concept of cause would have occurred within the juridical sphere. Man would have sought the cause in the order of human acts as the root of responsibility and imputability before considering it as a principle and constitutive element of the reality of being. According to Tannery (A. Lalande, *Vocabulaire critique de la philosophie*, I, p. 100, note), while the Greeks emphasized the initial juridical moment of "inquiry" and accusation (αἰτεῖν, αἰτία, αἰτία), the Latins insisted on the central moment of "defense" (cauere, causa), just as the Neo-Latin terms related to the Italian "casa" (house). An existential insight also noted by G. Marcel: "Imputability, or rather the need to impute (to have something or someone with whom to contend), would not in fact be at the origin of every causal explanation?" (*Être et Avoir*, Paris 1935, p. 8).
It was Aristotle, who well knew juridical usage (H. Bonitz, *Index*, 23 a 35), who provided the rigorous structure of the concept of cause (*Metaphysics*, V, 2, 1013 a 24 ff.). Cause is not merely a *principle*: a principle is what stands at the beginning of an order or a succession, whether in being, becoming, or knowing; cause, instead, is a principle of "dependence" and belongs properly to the order of reality. "Principium communis est quam causa... Principium ordinem quemdam importat; hoc vero nomen causa importat influxum quemdam ad esse causati" (St. Thomas Aquinas, *Commentary on the Metaphysics*, V, lect. 1, nn. 750-751). Nor is it to be confused with *reason*, which provides an explanation in the order of knowing; nor with *condition*, which is an extrinsic factor required for the cause to operate. As a "real" principle of being and becoming, the concept of cause does not have a uniform meaning. Aristotle enumerated four causes of being (*Physics*, II, 3, 194 b 16; 195 b 30; *Metaphysics*, loc. cit., and I, 3, 983 a 26-32; IX, 4, 1044 a 32 ff.): 1) Matter, the substratum or "potentiality" receptive of perfections or forms; 2) Form, the "act" and perfection that determines a thing to be what it is, constituting its essence or species; 3) The efficient cause, that "from which" the impulse to movement proceeds; 4) The final cause, the end for the sake of which the efficient cause acts. The first two causes are constitutive and therefore "intrinsic" to being, while the latter two are extrinsic to the effect they produce. Within each pair, one cause corresponds to the other. The causes in being are not juxtaposed but interpenetrate "causally": "Nam efficiens et finis sibi correspondent invicem, quia efficiens est principium motus, finis autem terminus. Et similiter materia et forma: nam forma dat esse, materia autem recipit" (St. Thomas Aquinas, *loc. cit.*, I, lect. 2, n. 775). Other divisions, which may apply to all four causes, include: cause *per se* and *per accidens*, first and second, immediate and mediate, direct and indirect. Each type of causality entails its own specific subdivisions. Christian philosophy, especially from St. Augustine onward, admits as the foundation of finite reality the extrinsic formal cause, or *exemplary* cause, which are the "divine Ideas" according to which each thing is brought into number, order, and measure.
The doctrine of the four causes certainly constitutes the culminating point and the most characteristic aspect of Aristotelian thought. In proposing it, Aristotle was convinced of having reduced into a complete and coherent doctrinal system the scattered indications found in his predecessors (*Physics*, II, 3, loc. cit., and I, 198 a 14 ff.). Some recent critics have accused Aristotle of having bent the thought of others to the aims of his own thesis, distorting history with the double gratuitous assumption that from the outset the problem of nature was treated as a problem of causality and that the conceptions of individual philosophers were nothing more than anticipatory fragments of his system rather than entirely different conceptions (H. Cherniss, *Aristotle's Criticism of Presocratic Philosophy*, Baltimore 1935, pp. 218 ff.). Whatever the case may be, the theoretical value of the doctrine lies in its intrinsic consistency. Aristotle, drawing on the "natural philosophers" for the concept of material cause, sought to ensure the concreteness of being; by placing, within matter, the "form" as the determining principle, he acknowledged with the Platonists the primacy of the intelligible and the spiritual, to which the movement of the entire universe remains suspended as to its first Mover and ultimate end (*Metaphysics*, XIII, 9, 1074 b 34). It is not becoming that explains being, but rather being that explains becoming insofar as its forms are arranged hierarchically according to the forms and degrees of causality. For this reason, in the scientific elaboration of Catholic doctrine completed in the 13th century, the Aristotelian theory was the preferred instrument, and many formulas, now consecrated by theology and dogma, reveal the Aristotelian origin and terminology.
In general, the application of the concept of cause requires caution regarding analogy, both with respect to the four types indicated and their subdivisions, because causality directly concerns being and therefore precedes the categories (q.v.). Strictly speaking, causality cannot be treated as a category, not so much or not only because categories are classifications easily accessible in experience, as Fr. Brentano believed (*Vom der mannigfachen Bedeutung des Seins*, Freiburg in Br., 1862, p. 194), while causes are the profound principles and therefore less known, but because causes are the very constitutive and productive principles of being and thus precede and, strictly speaking, have the character of "foundation" with respect to the "figures of the categories."
For Aristotle, as substance so cause is first and foremost something to be individuated and not universalized (*Physics*, II, 2, 194 b 13); "Nature" therefore does not represent a causality in itself, outside and above individual causes, as Hardy claimed, but is their order and complex (q.V. A. Mansion, *Introduction à la physique aristotélicienne*, Louvain 1913, pp. 50-51, 158; 2nd ed., 1914, pp. 59 ff., 266, n. 42). The theory of universal causes has as its corollary the devaluation of individual causes and is characteristic of Neoplatonism: outlined by Plotinus with the theory of the three Hypostases (the One, Intellect, Soul) and given a dialectical mechanism by Proclus in the triadic form of imparticipate, participated, and participative (E. R. Dodds, *Proclus, The Elements of Theology*, Oxford 1932, p. 210 ff.). Neoplatonism inspired, with different aims, both medieval thinkers through the famous opuscule *De causis* and the pantheistic naturalism of Giordano Bruno. In rationalism, cause is equated with "reason"; in positivism, with the mere spatio-temporal antecedent. In modern physics, the concept of cause tends to be replaced by that of "probability."
II. Principle of Causality.
The bond and real connection between cause and effect is called causality, and the affirmation of the necessity of such a connection is expressed by the principle of causality. The necessity of the connection can exist either on the part of the cause or on the part of the effect: in the first case, one has "necessary" causality, in opposition to "free" causality, and it is a particular case of causality. The principle of causality, in its most universal form, generally expresses the necessity of the real dependence of every effect upon a cause. The defense or rejection of this necessity has given rise to the most serious crises in human thought.
Aristotle expresses the principle in relation to the fundamental fact of nature, motion: “Every thing that is moved must necessarily be moved by something else” (Physic., VIII, 1, 241 b 34). The proof: “For if it does not have within itself the principle of motion, it is clear that it is moved by another; for what moves cannot but be something else” (loc. cit., 35–37). Based on this principle, Aristotle then proceeded to demonstrate the existence of the First Unmoved Mover, God.
The first form of causal skepticism in antiquity is attributed to the Pyrrhonians, among whom Enesidemus distinguished himself. Sextus Empiricus, however, attributes the absolute denial of causality to the Sophists; Enesidemus, on the other hand, would have considered causality among those things about which one can say both that they exist and that they do not exist (Adv. Mathem., IX [adv. dogmaticos, III], § 195, 207 ff.). The negative stance is supported first of all by the “ideal” character proper to the relation; but causality is a relation; it therefore has a purely ideal, not real, value. This logical argument is immediately reinforced by a more systematic one: “If causality exists, then either a body is of a body, or an incorporeal of an incorporeal, or a body of an incorporeal, or an incorporeal of a body...” But none of these hypotheses is possible, as Sextus shows (loc. cit., n. 210 ff.). Sextus further reports (Hypot. Pyrrhon., I, 17, § 180 ff.) eight “modes” or ways by which Enesidemus exposed the fallacies of those who defended the existence of causality, from which it is inferred that the opponents in view were the Stoics, for whom causality had to be something material.
Dialectical skepticism: Zeller (Die Philosophie der Griechen, III, II, 2nd ed., Leipzig 1868, p. 38) observes that in this critique the point that would agitate modern philosophy—the origin of the concept of causality—is not touched at all.
In the Middle Ages, among the Arabs, the mystical theologian al-Ghazālī denied the efficacy of creatures in order to safeguard the causality of God, foreshadowing the occasionalism of Geulincx and Malebranche. In Latin Scholasticism, nominalism effectively led to the denial of the principle of causality already in Ockham, followed by an ever-growing host of opponents of Thomistic Aristotelianism, whose foremost exponent was Nicholas of Autrecourt: skepticism predominantly logical. Nicholas asserts that from the existence of one thing (effect, creature) one cannot with absolute certainty infer the existence of another thing (the cause, God), whose negation would imply a contradiction (Epist. ad Bernardum, ed. Lappe, Münster in Westf. 1908, p. 8; ll. 15 ff.). Since the principle of causality affirms the necessity that one thing derive from another, the predicate would come to be outside the subject (“Consequens non esset idem cum antecedente, vel cum parte significati per antecedens,” loc. cit., p. 8, ll. 21). This, together with other philosophical errors connected with it, was condemned in 1346 (Denz.-U., esp. 558–60).
Decisive for the development of modern thought was Hume’s critique of causality; a gnoseological skepticism arising from the impossibility of explaining the origin of the notion of causality, in which the abandonment of causality is not so much the consequence as the ultimate foundation of universal theoretical skepticism. After having established, like the medieval skeptics, that one cannot a priori, by examining pure concepts (“ideas” of cause and effect), demonstrate the necessity of the principle, Hume asks whether there is any evidence for their origin in the immediacy of “impressions” (of sensation or reflection). In fact, however, experience presents only the simple succession of one phenomenon after another, never the communication of an active power and the necessity of causality. Therefore, the belief in causality lacks any foundation, whether a priori or a posteriori: the persistence of this belief and its real utility in human conduct is a mysterious process of nature whose secret we do not know (Treatise of Human Nature, pt. I, sect. 14a, ed. L. A. Selby-Bigge, Oxford 1928, pp. 157 ff.; Appendix, pp. 623 ff.). The Humean analysis of causality, tied to associationist psychology, has been vigorously rejected in our own day both by Gestalt psychologists (cf. K. Koffka, Principles of Gestalt Psychology, London–New York 1936, pp. 378 ff.) and by spiritualist psychologists (cf. A. M. Chotte, La perception de la causalité, Louvain–Paris 1946).
Kant, influenced by Hume’s critique, abandoned Leibnizian rationalism of sufficient reason and extended to all the principles of science, valid a priori, what Hume had said of the principle of causality (Prolegomena zu jeder künft. Metaphysik, Introduction, pp. 260–61, akad. Ausg.). The principle of causality is presented as the “second analogy of experience” and is described as a “principle of production, principle of succession in time...” (Kritik der reinen Vernunft, A 189, B 232–33). Causality is one of the twelve categories or pure concepts of the understanding and, as such, a function of the “I think” transcendental; the “schema” by which it applies to the real is the succession of the manifold insofar as it is subject to a rule (loc. cit., A 144, B 183). For Schopenhauer, the principle of causality becomes again “the principle of sufficient reason of becoming” (Über die vierfache Wurzel des Satzes vom zureichenden Grunde, ch. IV, § 20, Werke, ed. E. Grisebach, Leipzig 1891, vol. III, p. 47).
Kant’s position marked the turning point for further developments and the abandonment of the classical stance. A reflection of considerable importance was also seen in nosostatic philosophy when, at the end of the last century and the first decades of the present one, the question of the “analyticity” of the principle of causality was explicitly raised. While holding that the principle has a necessary and universal value, some vigorously denied that it could be called analytic (De Margerie, Viniati, Larmine, Sawicki, Hessen, Geyser...).
Even if the influence of Kant’s position in this entire controversy seems undeniable, it has brought to light a real difficulty inherent in the foundation of the principle of causality, namely that this principle concerns the structure of objective being as such and therefore demands a pronouncement on this objective reality. For some, indeed, the principle of causality depends on the principle of the intelligibility of the real; since this in itself is not evident and appears only as a “postulate” (Sawicki, Hessen), it follows that a finite uncaused reality may seem “unthinkable,” but this does not mean that it is therefore “impossible” (J. Hessen, Das Kausalprinzip, Augsburg 1928, p. 227). For others, the synthetic character of the principle is inherent in causality itself insofar as it is a process; as a process it implies development and therefore cannot be deduced a priori, but requires to be known in an immediate apprehension, in an intuition of its essence (Wesenschau) as such (J. Geyser, Das Gesetz der Ursache, Munich 1933, p. 23). Geyser’s position, which seeks to reconcile the two analytic and synthetic currents, consists of two moments: a) the direct intuition of a fact of succession, where succession is immediately grasped as causality and directly in the becoming and flow of the effect from the cause, and Geyser points to internal experience (monotono-phonological); b) the further extension of the causal relation, thus grasped, to all other cases of succession, which Geyser bases on the physical principle that “every phenomenon tends by itself to maintain itself indefinitely in its state,” so that any change in it does not come from the phenomenon itself but from something external to it (monotono-logical-metaphysical).
The defense of the analyticity of the principle by traditional philosophy has followed two paths. Although all agree in holding that the denial of causal dependence is not only unthinkable but also impossible—that is, contradictory and unreal at the same time—this contradictoriness (or “reductio ad absurdum” or “to the principle of contradiction”) some derive directly, others indirectly, by first reducing the principle of causality to that of sufficient reason and then this to the principle of contradiction (esp. R. Garrigou-Lagrange). Both have chosen different formulations of the principle that they consider more suitable for its critical justification, but they agree in the traditional position that the principle is absolutely valid within the realm of being as such and that this validity is justified by its solidarity (i.e., “reduction,” in logical language) with the principle of contradiction. In traditional
Principles are first principles of being and consequently principles of thought. Since the principle of causality concerns the becoming and the being of the finite and the multiple, it is, by the very nature of being itself, connected to the first principle of being, which is the principle of contradiction. In terms of Aristotelian-Thomistic logic, the principle must be called "per se known": that is to say, the requirement of the predicate is inherent in the subject, and our knowledge of the predicate necessarily derives from our knowledge of the subject. This derivation can be twofold: either of the first degree ("propositio per se nota primo modo"), as occurs in all elements of the definition that are strictly essential; or of the second degree, when it concerns properties that directly and necessarily follow from the essence. According to St. Thomas, the principle of causality falls into the second category:
"The relation to a cause does not enter into the definition of a being that is caused, yet it follows from those things that belong to its essence; because from the fact that something is a being by participation, it follows that it is caused by another. Hence, such a being cannot but be caused; just as man cannot but be capable of laughter. But because being caused is not part of the essence of being simply speaking, for this reason we find some being that is uncaused" (Sum. Theol., 1a, q. 44, a. 1 ad 1).
The formula of participation constitutes, in Thomistic metaphysics, the definitive expression of causal dependence. It expresses the ultimate relationship between God and the creature, between substance and accident... that is, the dependence of being in the expression of maximum conceptual purity (the notion of participation), in which dependence, likeness, and distinction converge at the same time—all characteristics proper to the effect in relation to its cause, and which no other notion is able to express in this way. In the Thomistic position, then, the complicated controversy in which much of neo-scholasticism has been embroiled, and not always with the best results, has no place, but is explained by the fact that various formulas, more or less unsuited to the strictly critical-metaphysical exigency of the defense, were chosen for the critical defense of the principle of causality.
The definitive critical formula of the principle of causality must:
a) embrace all that is in some way caused;
b) immediately express the dependence of the effect on the cause.
Among the formulas that have enjoyed the greatest vogue in the discussion (it is unnecessary to mention: "omnis effectus habet causam," because "effectus" already says what is caused and is therefore useless for the discussion, and if it does not say this, it must rely on other concepts), the most important are the following:
1) *Omne quod movetur ab alio movetur.* A strictly Aristotelian formula (Phys., VII, 1, 241 b 34) and adopted by St. Thomas as the foundation of the first way for the demonstration of the existence of God (Sum. Theol., 1a, q. 2, a. 3), but by that very fact limited to a precise sector of caused things, namely that of motion.
2) *Omne quod incipit exigit causam.* This is the formula preferred by Hume, but it is also found in St. Thomas, who, as is well known, did not consider the beginning to be and being created as such to be inseparable, and admitted the possibility of creation "ab aeterno." It cannot therefore represent the definitive formula.
3) *Omne quod est in potentia non fit (actu) nisi per aliquod ens actu.* An Aristotelian formula (cf. Met., IX, 8, 1049 b 24) that provides the metaphysical foundation of the two preceding ones and rests on the two cornerstones of the philosopher’s metaphysics, though he intended them only in function of natural becoming without reaching the first origin of beings from God, and of pure potency (prime matter) from pure act (God).
4) *Omne contingens (quidquid contingenter existit) habet causam.* This is the formula that has enjoyed the greatest favor among neo-scholastics (Garrigou-Lagrange, Droege, Boyer, Descoqs) and is certainly not foreign to Thomism, since even for Aristotle being is divided into contingent and necessary (cf. Met., V, 5, 1015 a 20 ff.). "Contingens" corresponds to the "possibile esse" used by St. Thomas in the third way, but in Thomistic metaphysics this "contingent" coincides with material reality subject to generation and corruption and cannot therefore occupy the place of being as such that is caused. For the Angelic Doctor, who in metaphysics resumes a terminology that Aristotle uses in logic (for conclusions derived from necessary premises, Met., V, c. 1015 b 9-11), there are necessary things that have a cause of their necessity, that is, they are caused "ab alio," which is necessary by essence (cf. C. Gent., II, 30: *Qualiter in rebus creatis possit esse necessitas absoluta*; C. Fabro, *Intorno alla nozione tomista di contingenza*, in Riv. di filosof. neosc., 30 [1938], p. 132 ff.).
5) *Omne compositum indiget causa componente.* This formula truly embraces every created being and is frequently found in St. Thomas (cf. the full enunciation in: Sum. Theol., 1a, q. 3, a. 4). In its ultimate metaphysical scope, it points to the first composition of finite being, that of essence and act of being, in which the condition and the first effect of creation itself are manifested. And creation is held by St. Thomas to be demonstrable, and is demonstrated by him with the principle of participation (Sum. Theol., 1a, q. 44, a. 1), just as with the same principle the Angelic Doctor demonstrates the real distinction between essence and act of being (Quodlib., II, q. 2, a. 3). Of the two moments of participation, as causal dependence and real composition, it seems to us that in our process of critical-metaphysical justification of the principle of causality, participation as causality comes first, and then, in dependence on this, the further determination of the creature as a reality of composition. Such is the constant method followed by St. Thomas (cf. C. Fabro, *La nozione metafisica di partecipazione...*, Milano 1941, p. 216 ff.), and it is the only one that goes to the root of the problem. The notion of participation, by reason of its metaphysical purity, lends itself at once to all the nuances of analogy (v.) to which the notion of causality is subject, both in the fourfold division of causes and in the distinction between infinite causality (according to being, proper to God) and the manifold actualizations of finite causality (according to becoming, proper to finite agents).
It may be added that in his notion of participation, St. Thomas saw the perennial truth of Platonism and Aristotelianism converge (cf. *De subst. sep.*, c. 3), and that in it the very basic conception of Aristotelian metaphysics, that of act and potency, finds that definitive resolution which allows one to escape both dualism (of absolute separation) and acausalism (God as merely final cause, not productive of the world), of which the Aristotelian theory has been repeatedly accused from the Fathers down to our own day. Moreover, the notion of participation does not seem alien to allowing some appropriate insertions of Christian thought to satisfy those legitimate exigencies of modern thought that may arise in conceiving the structure of the subjectivity of spiritual being.
The dependence of the finite on the infinite; provided this is done with the cautions used by the Angelic Doctor, avoiding the excesses of some of his disciples (Eckhart, Dietrich of Freiburg). This notion is the foundation of the fourth way, which is generally considered the most important for the demonstration of the existence of God. As St. Thomas says in the Prologue to the *Lectura in Ioannem* (Parm. ed., vol. X, col. 280 a), it is proper to the Platonists “who came to the knowledge of God from the dignity of God Himself.”
The formula of participation therefore seems best suited to satisfy the conditions of universality and immediacy required by the critical formulation of the principle.