Scholastic Metaphysics

1.  Act and potency

1.1  The general theory

1.1.1  Origins of the distinction

The first of the famous twenty-four Thomistic theses reads:

Potency and act are a complete division of being. Hence, whatever is must be either pure act or a unit composed of potency and act as its primary and intrinsic principles. (Wuellner 1956, p. 120)

The distinction between potency and act is fundamental not only to Thomism but to Scholastic philosophy in general (though as we will see, Scotists and Suarezians disagree with Thomists about how to interpret the distinction). It is absolutely crucial to the Scholastic approach to questions about the metaphysics of substance, essence, and causation (and for that matter to Scholastic philosophy of nature, philosophical psychology, natural theology, and even ethics). We would do well to begin, then, with an outline of the theory of act and potency. Subsequent sections of this chapter and the next will develop and defend key aspects of the theory as they apply to causation. In later chapters we will see how the theory applies to other metaphysical issues.

The theory has its origins in Aristotle’s account of where the Eleatics on the one hand, and Heraclitus on the other, went wrong in their respective positions vis-à-vis change versus permanence -- an account that was extended by Scholastic writers to a critique of the Eleatic and Heraclitean positions vis-à-vis multiplicity versus unity.

Parmenides and Zeno denied the reality of change. Parmenides’ position is essentially that (1) change would require being to arise out of non-being or nothingness, but (2) from non-being or nothingness, nothing can arise, so that (3) change is impossible. Zeno aimed to reduce the notion of local motion to absurdity via paradoxes some of which presuppose that traversing a finite distance would require traversing an infinite number of shorter distances. For example, in the dichotomy paradox, Zeno suggests that a runner can get from point A to point B only if he first reaches the midpoint between A and B; but he can reach that midpoint only if he first reaches the point midway between A and the midpoint, and so on ad infinitum. Hence he can never reach B, and indeed can never even move beyond A.

A natural first response to such arguments would be to apply the method of retorsion and argue that those who deny the reality of change are led thereby into a performative self-contradiction. The Eleatic philosopher has to move his lips or pen in order to put his argument forward; if he bites the bullet and denies that even his lips and pen are really moving or that he is really trying to change the minds of his listeners or readers, he still has to go through the steps of his reasoning in his own mind, and that involves change. The reality of change is not self-evident, insofar as it is not a necessary truth that any change ever actually occurs. But it is still evident insofar as we have to acknowledge it in order to argue for anything at all. (Cf. Smith and Kendzierski 1961, p. 16)

This tells us at most that something has gone wrong in the Eleatic arguments, but not what, exactly, has gone wrong. The problem with Parmenides’ reasoning, in Aristotle’s view, is neither in the inference from (1) and (2) to (3), nor with premise (2), with which Aristotle agrees. It is rather with premise (1), the thesis that change would involve being arising from non-being. For there is, according to Aristotle, an alternative analysis of change, on which it involves, not being arising from non-being, but rather one kind of being arising from another kind. In particular, there is being-in-act -- the ways a thing actually is; and there is being-in-potency -- the ways a thing could potentially be. For instance, a given rubber ball might “in act” or actually be spherical, solid, smooth to the touch, red in color, and sitting motionless in a drawer. But “in potency” or potentially it is flat and squishy (if melted), rough to the touch (if worn out through use), light pink (if left out in the sun too long), and rolling across the ground (if dropped).

These potentialities or potencies are real features of the ball itself even if they are not actualities. The ball’s potential flatness, squishiness, roughness, etc. are not nothing, even if they do not have the kind of being that the ball’s roundness, solidity, smoothness, etc. currently have. That is why the ball can become flat, squishy, and rough in a way it cannot become sentient, or eloquent, or capable of doing arithmetic. Being-in-potency is thus a middle ground between being-in-act on the one hand, and sheer nothingness or non-being on the other. And change is not a matter of being arising from non-being, but rather of being-in-act arising from being-in-potency. It is the actualization of a potential -- of something previously non-actual but still real.

Zeno too overlooks the distinction between being-in-act and being-in-potency. The infinite number of smaller distances in the interval between two points A and B are indeed there, but only potentially rather than actually. Hence there is no actually infinitely large number of distances the runner must traverse, and Zeno’s purported reductio fails.

Heraclitus had (on a traditional interpretation, anyway) gone to the opposite extreme from that of the Eleatics, holding that there is no being but only endless becoming. Change and change alone is real -- the implication being that there is no stability or persistence of even a temporary sort, nothing that corresponds to Aristotle’s notion of being-in-act. Here too the method of retorsion might be deployed. If there is no stability of any sort, how could the Heraclitean philosopher so much as reason through the steps of his own argument so as to be convinced by it? For there will on the Heraclitean view be no persisting subject, so that the person who reaches the conclusion will not be the same as the person who entertained the premises. (Cf. Geisler 1997, pp. 65-66) Nor will there be any such thing as “the” argument for his conclusion -- some single, stable pattern of reasoning which the Heraclitean might rehearse in his attempts to convince his critics, or even repeat to himself on future occasions.

Nor is there, in the Aristotelian view, any sense to be made of change in the first place except as change toward some outcome, even if only a temporary outcome. The ball melts, but this is not merely a move away from roundness and solidity; it is a move in the direction of squishiness and flatness, and thus in the direction of new actualities. Moreover, such changes occur in repeatable patterns. This or that particular instance of roundness or flatness comes and goes, but new instances of the same features can and do arise. Hence the changes that occur in the world in fact reflect a degree of stability that belies Heraclitus’ doctrine of flux, even though it does not approach the absolute stasis of the Eleatics.

The Eleatic and Heraclitean extremes vis-à-vis change and permanence are paralleled by similar extremes on the question of multiplicity versus unity. Parmenides denies that there can possibly be more than one being. For if a being A and a purportedly distinct being B really were distinct, there would have to be something to differentiate them. But since A and B both are, by hypothesis, beings, the only thing that could do so would be non-being; and non-being, since it is just nothingness, does not exist and thus cannot differentiate them.

Zeno reaches a similar conclusion via his paradox of parts. If there is more than one being, then either these multiple beings have size or they do not. If they do not, then since things of no size can, even when combined, never yield anything with size, it would follow that there is nothing of any size at all, which is absurd. But if these multiple beings do have size, then they are infinitely divisible and thus have an infinite number of parts. And if they have an infinite number of parts, then they must all be of infinite size, which is also absurd. So there cannot be more than one being.

The Heraclitean position, by contrast, when pushed to the extreme would entail that there is only multiplicity and no unity in the world, nothing to tie together the diverse objects of our experience. There is this particular thing we call “round,” that one, and a third one, but no one thing, roundness, that they all instantiate; there is this perceptual experience of what we call a “ball,” that one, and a third one, but no one thing, that ball itself, that these experiences are all experiences of, and no one subject, the perceiving self, which has the various perceptual experiences. (To be sure, Heraclitus himself adopted a kind of monism on which there is one thing, the world itself, which is the subject of endless change -- a dynamic monism rather than the static monism of the Eleatics. Still, none of what J. L. Austin called the “middle-sized dry goods” of everyday experience could count as unified subjects on this view.)

Once again the method of retorsion might be deployed against such views. If, as the Eleatics claim, there is in no sense more than one being, then how can the Eleatic so much as distinguish between himself and his interlocutor, or his premises and his conclusion? How can...