POTENCY AND ACT

Separate studies on potency and act are demanded if one is to gain a knowledge of their significance and the range of their application. But these leave something to be desired. Since they isolate the notions from one another, they offer a static picture with only suspicion of the dynamic quality of potency and act. To supply this quality, one must seek a situation in which the two notions are involved in intimate relationship. This is found in the context of being that does not exceed the limits of the predicamental order (see categories of being). For it is of this being that potency and act are principles (see principle).

In such a context potency and act reveal themselves for what they are entitatively. They are simply principles, not things. Both are essentially incomplete, since neither is able to claim more than an imperfect participation in the form of being, Furthermore, they are naturally corroborative. Potency is the indetermined and perfectible element that looks to act as its determinate and perfecting complement. Because of their imperfect grasp on the form of being, the two necessarily require mutual assistance to exercise their role as principles of an existent. (For an exception, however, see soul, human, 4.)

Origin with Aristotle. It is Aristotle who must be credited with the discovery of the notions of potency and act. Initially it was his concern with the problem of change that provided the occasion for the discovery (Phys. 184a 9–192b 5). Prior to his time change was conceived as limited to the order of accidents; all the early naturalists steadfastly denied that it ever penetrated to the level of substance. Moreover, for them it was more a case of unveiling what was actual but hidden than of discovering the nature of change itself (see Saint Thomas Aquinas, In 1 phys. 9.2–3). With Aristotle's discovery of the notion of potency and his projection of that notion to the substantial order in the concept of primary matter, the whole picture was altered (see matter and form). A true science of change was initiated. But important as this is, it is far from being the only application of the notions of potency and act in Aristotelian philosophy.

The further one ventures into the corpus of Aristotle's natural studies, the more evidence one encounters of the significance of these principles. These are, one learns, the basis of the theses that constitute the heart of his philosophy of nature and his psychology, such as, for example, the definition of motion (Phys. 201a 10) and that of the soul (Anim. 412a 6–28). But it is in his Metaphysics (1017a 35–b 9; 1045b 28–2052a 12) that Aristotle explicitly extends their horizons by bringing potency and act into the focus of being itself. Here he gives them a distinctively metaphysical aspect and lays the groundwork for the special use to which medieval philosophers would put them in their teachings concerning essence and existence.

Thomistic Development. With the ascendancy of aristotelianism among the schoolmen, the doctrine of potency and act assumed great prominence in scholastic philosophy. But while all made it a major feature of their respective systems, none equaled Saint thomas aquinas in his fidelity to Aristotle's concepts or in the role he granted them in his philosophy. Whereas other outstanding figures, such as Duns Scotus and F. Suárez, adulterated the Aristotelian notions of potency and act, Saint Thomas preserved them in their original purity and made them the cornerstone of his philosophy of being. Special topics that deserve mention in that philosophy are the real distinction between the concepts, their relative priority, the limitation of act by potency, and the distinction between essence and existence.

Real Distinction. There are instances in which the actual separation of act and potency prove beyond doubt the reality of their distinction. It must be admitted, however, that such instances are too few and are verified in too limited a context (that of the soul's operative powers) to constitute a premise warranting a universal conclusion. It is for this reason that Thomists look in a new direction for a compelling proof, namely, to the conceptual order.

While aware that not every conceptual distinction is an actual reflection of the ontological order (e.g., the distinction between the concepts of genus and difference is a case in point), Thomists argue that the extensive distance between the concepts of potency and act is a proof of their real distinction. The concepts of potency and act far exceed the distance that separates concepts that are virtually distinct by a virtual major distinction, as is the situation with regard to the concepts of genus and difference (see distinction, kinds of). The latter share a commonness despite their distinction. Both signify the totum: the genus indeterminately, the difference determinately. Neither signifies a wholly new form but rather the same form, the sole variation arising from the mode of signifying. Consequently, their distinction, while having roots in the reality they represent, does not pass over from the conceptual to the ontological order. The case of the concepts of potency and act is altogether different. The concept of each stands diametrically opposed to that of the other, and there exists no ground on which this opposition can be resolved. The concept of potency formally signifies capacity or the absence of perfection, whereas that of act signifies perfection. Thus potency formally negates the very substance of act. Granting the correctness of each concept, it necessarily follows that the one and the other signify notions that defy identification, and this not only conceptually but also ontologically.

Relative Priority. In the order of knowledge, act naturally is prior to potency. Because potency signifies possibility and the measure of the knowableness of an entity depends on its actuality (In 1 phys. 1.7), potency can be known only through the act that is its fulfillment (In 9 meta. 7.1846).

In the ontological order, in which potency and act are constituent principles, potency is in most cases anterior to act. This follows because potency is generally the subject of act and therefore must be prior to it in time or solely in nature, or both in time and in nature. If one considers the matter absolutely, however—i.e., without reference to the circumstances associated with potency and act as constituent principles of being and attending solely to their respective natures—one must acknowledge the priority of act over potency. The reason for this is that the only source that can effect a transfer from potency to act is a being that is already in act (see motion, first cause of).

Limitation of Act by Potency. The multiplication of act affords sufficient proof of the compatibility of the notions of limitation and of act. But the source of the compatibility is not quite obvious. Can the two notions be immediately joined or must they be mediated? Saint Thomas's answer is constant: the two notions can be associated only through the medium of potency.

Three alternatives suggest themselves as explanations for the limitation of act: act itself, potency, and the efficient cause. The first and third alternatives must be excluded. Were act self-limiting, it would negate itself, for it would be forced to assume a contradictory character, i.e., that of presenting itself as the principle of a perfection and of its negation. Similarly, appeal cannot be made to the efficient cause. It is not within the competence of this cause, be it infinite or finite, to resolve a natural incompatibility such as exists between the notions of act and self-limited act. There remains, then, potency as the final possibility, and here Thomists find the principle of act's limitation. The explanation follows from the nature of potency itself. Potency is self-limiting; it is a capacity for a definite act. Possessed of this inherent limitation, it naturally imposes limitation upon the act it receives; whatever is received must be received according to the measure, or limiting capacity, of the recipient (see participation).

Essence and Existence. The notions of potency and act provide maximum service within Thomism for solving the problem of the relationship between essence and existence. Other arguments can be given as a basis for maintaining the real distinction between essence and existence, but the doctrine of potency and act here assumes the greatest cogency. In particular, the Thomistic analysis of the nature of act and of its principle of limitation furnishes the middle term through which the real distinction between essence and existence is demonstrated (see essence and existence).

Later Scholasticism. One finds in the philosophy of the schoolmen a strong echo of Aristotle's evaluation of the importance of potency and act. Every major system of metaphysics elaborated within the scholastic tradition, whether of Thomist, Scotist, or Suarezian persuasion, places major emphasis on these notions. But while Aristotle's influence is far from negligible, it would be erroneous to see the thought of the scholastic tradition as a mere copy of that of the Stagirite. For one thing, a new use was made of potency and act by the scholastics; for another, though it is debatable whether this was a development, the Aristotelian notions came to be greatly modified.

The Thomistic application of the notions of potency and act to the problem of essence and existence, for example, was a wholly new venture. Though Aristotle himself did employ potency and act in his study of being, he did not consider the question of essence and existence in the context of the actual existent, nor did he apply the doctrine of potency and act to its general resolution. This was left to the scholastics, especially those of the Thomist school (see thomism).

Notable but regrettable changes in the structure of potency and act were much in evidence in both the Scotist and Suarezian systems. John Duns Scotus expanded the structure by attempting to introduce an intermediate between potency and act, viz, the notion of virtual act. F. suÁrez, in his turn, conceived of potency as an actus imperfectus, thereby restricting, rather than expanding, the traditional structure. These changes were significant. With the introduction of virtual act Scotus felt compelled to challenge the universality of the distinction between the moved and the mover (Opus oxon. 2.25.1.12), and consequently the metaphysical character of Saint Thomas's prima via. Suárez's interpretation of potency as an actus imperfectus had similar repercussions. Because of it he was forced to deny the basic opposition between potency and act in the systems of both Aristotle and Saint Thomas. Furthermore, he had to reject the principle "whatever is moved is moved by another" as not having metaphysical validity (see scotism; suarezianism).

Modern Thought. So long as modern thought followed the pathways of idealism or empiricism in any of their variations, the doctrine of potency and act could not hope for any type of recognition. The philosophical neglect of these principles varied in direct proportion to the rejection of realism, whether this was its complete repudiation, as in idealism, or merely its limitation to the sensibly perceived, as in empiricism.

In contemporary philosophy, however, a new interest in realism has begun to emerge. Rejecting idealism's attempt to impose its own image on the world of things, existentialists have become absorbed with the anguish of existence. Their concern with existence, although presently fettered with the chains of irrationalism, could ultimately open the way for a renewed interest in potency and act (see existentialism).

See Also: potency; act; essence and existence; matter and form

Bibliography: j. m. ramirez, De ordine, Placita Quaedam Thomistica (Salamanca 1963). g. m. manser, Das Wesen des Thomismus (3d ed. Fribourg 1949). a. forest, La Structure metaphysique du concret selon S. Thomas d'Aquin (Paris 1956). p. descoqs, Essai critique sur l'hylémorphisme (Paris 1924).

[j. c. taylor]