Aristotle

How does Aristotle explain change' “All men by nature desire understanding.” This is how Aristotle opens his famous Metaphysics, one of the greatest philosophical works ever produced. The thirst for knowledge has always occupied Western man at least since the time of Thales, and even though many different views and opinions about what knowledge is and how it can be gained have abounded throughout Western philosophy up to this very day, the fact that so many men have dedicated their lives to seeking knowledge on all sort of different planes is evidence that the quest for knowledge has occupied a supreme position among human endeavors from the earliest times. To Aristotle it was clear that “though all men desire to know, there are different degrees of knowledge.” Wisdom is such that that it can “tell [us] what things are and why they are”; it tells us about a thing’s first principles and causes. Surely, then, in order to come to such a high level of knowledge, one must practice a particular science which concerns itself with just such first principles and causes—and this science Aristotle called “metaphysics.” Unlike the other sciences, metaphysics studies what exists as such, that is “being qua being,” as the traditional formulation has it. In his aspirations for wisdom, then, Aristotle engaged in metaphysics. His zeal resulted from the wonder, the aporía, which his predecessors had shown, and which intrigued him just as much. Aristotle was convinced, however, that his predecessors’ philosophies were incomplete and inadequate, especially as far as the paradox of change was concerned. The problem of change which the ancient philosophers faced is simply the following: “If we say that A changes to B, we seem to be saying that A is both itself and not itself. It must be A, for we say, ‘A changes’; it cannot be A, because we say it is B. If water is water, it is not ice; if it is ice, it is not water.” Aristotle was resolved to master this enigma once and for all, but, unlike Parmenides or Plato, he wanted to do it in a way consistent with empirical reality. Nature, according to Aristotle, is an inner principle of change and being at rest. This means that when an entity moves or is at rest according to its nature reference to its nature may serve as an explanation of the event. The nature of the entity is in and of itself sufficient to induce and to explain the process once the relevant circumstances do not preempt it. Nature as inner principle of change and rest is contrasted with active powers or potentialities (dunameis), which are external principles of change and being at rest, operative on the corresponding internal passive capacities or potentialities. Because motion or change (kinêsis) is mentioned in the definition of nature, any discussion of nature will need to rely upon the explanation of motion. When he submits that there is no motion besides the categories, he does not assign motion to the categories of action and passion. Aristotle speaks about four kinds of motion and change only; those in substance, in quality, in quantity and in place. Within the four domains where genuine change can occur, change always requires the existence of a potentiality which can be actualised. But change is neither identical to this potentiality, nor to the lack of a property, nor, without further qualifications, to the actuality which is acquired when the potentiality is actualised. The definition of motion suggests that such processes can be characterised in terms of a property or state of an entity, acquired as a result at the end of the process, which can be labelled the form within this process, and an initial lack of this form. Furthermore, Aristotle claims, there is a third component, which is not changed in the process, the substrate or subject of the motion. The presence of the potentiality can, nevertheless, be in accordance with the nature of the object—in which case the change is natural (phusei) or according to nature (kata phusin), or can happen in the face of a contrary disposition on the part of the nature of the entity—in which case the change is forced (biâi) or contrary to nature (para phusin). First of all, these motions or changes occur at the interaction of two potentialities. One, the passive potentiality, is in the object undergoing change, while the other, the active potentiality, is in the entity initiating change. The two potentialities need to match each other: when there is a potentiality for being heated in the object undergoing change, the process needs to be initiated by another object possessing an active potentiality for effecting heat. This is true to the extent that Aristotle can claim that the definition of passive potentiality is dependent on that of the active potentiality. These two potentialities need to work in tandem, and consequently Aristotle can claim that there is only a single process going on, which is located in the entity moved. Even though the foregoing might have suggested that generation of substances is fundamental for all the other kinds of changes, in fact locomotion will have a privileged status. All other changes depend on locomotions, because any two entities involved in change, with their active and passive potentialities respectively, need to come into contact in order for the interaction to occur. To explain how change occurs, Aristotle reflected on how we know things. It was clear to him that a thing is best known when we do not merely know what color, size, or shape it has, but when we know what it is. Thus, the mind distinguishes “a thing from all its qualities and focuses upon what a thing really is, upon its essential nature.” This substratum Aristotle called ousía, “substance,” and it is this in particular with which metaphysics concerns itself. Aristotle defined substance as “that which is not asserted of a subject but of which everything else is asserted.” For Aristotle, then, all individual things are substances. Now, Aristotle believed that all substances have two aspects: they are necessarily composed of “matter” and “form”—they are “hylomorphic.” By “form,” Aristotle meant the “properties [a substance] shares with other particulars” (e.g. being human or being a horse), whereas by “matter” he denoted the thing’s individuality—“that about it which makes it this horse or this man.” Neither matter nor form can exist all by itself; that is, we do not find in the world formless matter or matterless form. This is the reason why all substances are hylomorphic for Aristotle. With this novel doctrine of substance, Aristotle had already made some progress in his quest for explaining change, but this was only a prerequisite to a more elaborate theory. He observed that “substances develop through time” and so there seems to be a sort of movement, or striving, in every substance, which he called “entelechy.” This fact led Aristotle to redefine form and matter as actuality and potentiality: “In order to think effectively of a substance as it endures, yet changes, we must reinterpret matter and form as potentiality and actuality.” What a substance is really or actually right now is its actuality—for instance, I am sitting on an actual chair. Yet, what a substance has the prospect to become is its potentiality—for instance, an actual boy is a potential adult. What is crucial to this notion is that whatever possesses potentiality must possess actuality; that is to say, in order for there to be a potential Y, there must be an actual X. There is no such thing as pure potentiality, for in order for anything to be able to become something else, it must be something already. Armed with his conceptions of hylomorphic substance, potentiality, and actuality, Aristotle was finally able to make sense of the intriguing phenomenon of change: The individual A turns out on analysis to be a complex; it is a substance, a formed matter. During its change into B some part of A endures unchanged and some part of A alters. What endures is A’s matter; what changes is its form. This, then, is how Aristotle could explain how a chunk of marble could eventually become a statue. Its form was changed while its matter remained the same—its potential to be a statue was actualized. With this account of change, Aristotle was able to make sense of change and explain substances to a certain extent. However, he still wondered if not perhaps other questions could be asked about substances. The responses to these questions Aristotle entitled “causes.” What we mean nowadays by “cause” is usually an event that precedes an effect, but here the word “cause” is used in a looser sense than we moderns are used to; it means essentially “reason for being” or “explanation.” For Aristotle, then, there are four causes, or reasons, for everything that exists. We can ask at least four questions concerning any entity, and the answers we get will give us a better understanding of the being we are investigating. These four questions can be asked concerning anything, and the responses to them “represent therefore a broad pattern or framework for the total explanation of anything or everything.” Aristotle’s four causes are traditionally classified as “(1) the formal cause, which determines what a thing is, (2) the material cause, or that out of which it is made, (3) the efficient cause, by what a thing is made, and (4) the final cause, the ‘end’ for which it is made.” To use a classic example, let us apply these four causes to an object of art, say, a statue. In the order just listed, the four causes would be: “(1) a statue (2) of marble (3) by a sculptor (4) for a decoration.” However, the four causes do not just apply to man-made artifices; they can also be used to explain “natural objects, in which no conscious purpose is at work,” and so it is clear that for Aristotle, the four causes can be predicated of anything whatsoever. The formal cause denotes the essence of a thing, or its form—it is that which a thing strives to be. In the case of a work of art, it exists both in the mind of the artist, who is the efficient cause, as well as in the matter, the material cause, itself. To go back to our example of a marble statue, the “statueness” must exist first in the mind of the sculptor and also somehow in the marble, or else there would not be a marble statue in the end. The final cause, on the other hand, is a cause in terms of the end for which something is made or done. It was perhaps the insight of Plato which motivated Aristotle to ask for a purposeful end, or télos, as it is called in Greek, concerning entities in the world. Statues, for instance, are usually made for some end—for decoration, beautification, or some religious purpose. After all, no one makes a statue for no reason. It is in this sense that we are to understand the final cause. But again, just like the other causes, the final cause does not apply merely to human artifacts but also to natural objects, such as plants. For Aristotle, even entities like flowers and trees had a particular end to which they were striving. It may now be evident that this notion of final causality, of the télos of things, is inherently connected with Aristotle’s conception of potentiality, for if “the end of an acorn is to be a tree, in some way the acorn is only potentially a tree but not actually so at this time,” and thus by realizing its final cause, the acorn becomes an oak tree by actualizing its potential. Aristotle's classification of motions into those contrary to nature and those according to nature applies not only to the motions of the moved objects, but transfers also to the movers effecting motions. A mover can effect a motion which is contrary to its own nature. Aristotle's example of such an unnatural mover is the lever, an object heavy by nature, with which loads can be lifted. Although such movers can effect motions in the contrary direction to the motion at the head of the causal chain (levers are operated by the downward push of something heavy at the other end), the crucial consideration for Aristotle in this case is that the original, initiating cause of the causal chain should effect the motion according to its nature. In cases of forced motion, movers are present in a perspicuous way. This need not be so, however, in cases of natural motion. Once it is established that there is a mover for each change, the finite causal chains can be followed up to the primary instance of motion, the celestial revolutions, the Sun's motion along the ecliptic course responsible for many sublunar changes, the rotating seasons being foremost among them. Whether the cosmos has unmoved or moved movers, moreover, whether the universe is causally closed or needs some continuous external causal influence for its preservation, depends ultimately, then, on the status of the celestial motions.