The Four Causes
Aristotle, as he himself tells us, was the first philosopher to identify all four kinds of causes. Each cause is a different kind of answer to the question “why?” There are four kinds of answers to this question (i.e. answers which identify the matter, form, source and end).
Thus, to the question, “why is this a statue?”, Aristotle can give four sorts of answers: This is a statue because it is made of marble; because it is in the shape of David; because Michelangelo sculpted it; because Michelangelo wanted to depict the figure of David in marble (because he needed the money, perhaps). An account of each kind of cause is important for a fully scientific account of whatever a philosopher is explaining. Aristotle developed his account of the four causes from his analysis of change. (Click here for a summary of this analysis of change).
In every change there is, first of all, something that receives a new determination. Before undergoing the change, it is in potency to a new determination; then under the action of an efficient source it receives a new actualization. The marble upon which the sculptor works is in potency to receiving the new determination which the sculptor gives it. This new determination is the form of the statue. This example of marble receiving the form of the statue is a case accidental change, since what comes to be is a new accidental form (the shape) in what is already a substance (the marble). There are also cases of substantial change, that is, cases of new substances coming to be. Aristotle calls this kind of change generation and corruption. For example, when I eat an apple, the apple stops being an apple and becomes part of me. The other principal case of substantial change occurs when any plant or animal (which is a substance) ceases to be what it was. That is, the death of an animal, for example, is a substantial change, since the corpse (a collection of substances without any cohesion) comes to be from what previously did have cohesion (a living animal). On this view, substantial changes are occurring all the time in nature, as new substances come to be by generation, and old substances pass away, by being eaten, or simply by dying and decomposing.
Since it seems that anything might ultimately change into anything else, Aristotle postulated that there is an ultimate stuff that underlies the radical potency of everything (eventually and theoretically) to turn into anything else. And since Aristotle calls whatever is the bearer of potency the ‘matter’ in any change, this ultimate stuff is called ‘prime matter.’ Prime matter, in its own theoretical self, is without any determination but is mere potentiality as such. This is not to say that prime matter is ever the immediate and direct subject of a change on which any actual agent acts. It exists only in actual determinate things, as the radical potency to undergo limitless changes. Prime matter is only and always found with some substantial form that gives it determination. Yet, although it is never exists in and of itself, prime matter is real; it is a real principle of change. It is the real potency that every material thing has to undergo an indefinite amount of change.
We should not, therefore, say that prime matter is the simplest bodies of the material sublunary world; the four elements, earth, air, fire and water, themselves contain contraries and can be transmuted into one another. But if they change, then they presuppose composition of potentiality and act. Air, for instance, is air, but can become fire. It has the form or actuality of air, but it also has the potentiality of becoming fire. But it is logically necessary to presuppose, prior to the potentiality of becoming fire or any other particular and definite kind of thing, a potentiality for becoming at all, i.e. a bare potentiality.Frederick Coppleston, A History of Philosophy, Volume I: Greece and Rome, (NY: Doubleday, 1985), 307-308.
Modern nuclear physics tells us that the matter of every thing can ultimately and theoretically be converted into energy, and energy can similarly be converted into matter. Nevertheless, there still seems to be some principle that underlies each of these two ways of being physical but cannot exist without being one or the other, matter or energy. Thus, it seems that we still have a theoretical need for the notion of prime matter.
Each and every individual thing is composed not only of matter, but also of form. Form is the principle of determination which accounts for the thing being the kind of thing it is. As matter is the principle of potentiality, of the ability to become other than it is, form is the principle of actuality, of the thing being the sort of thing it is. In natural things, the substantial form is specifically the same for all members of the same species. That is, the substantial form of a thing accounts for it being the sort of thing it is, for belonging to the species to which it does belong. Thus, substantial form, considered apart from any matter in which it resides, is universal. Although form connotes shape or configuration, Aristotle means by form something more.
But in the case of living things, it is very clear that to explain behavior we must refer not to surface configuration, but to the functional organization that the individuals share with other members of their species. This is the form; this, and not the shape remains the same as as long as the creature is the same creature. The lion may change its shape, get thin or fat, without ceasing to be the same lion; its form is not its shape, but its soul, the set of vital capacities, the functional organization, in virtue of which it lives and acts…. A corpse has the same shape as a living man; but it is not a man, since it cannot perform the activities appropriate to a man (PA 640b30-641a17). When I ask for the formal account of lion behavior, I am not, then, asking just for a reference to tawny color or great weight. I am asking for an account of what it is to be a lion: how lions are organized to function, what vital capacities they have, and how these interact. And it is this, again, rather than an enumeration of its material contituents, that will provide the most simple, general, and relevant account for the scientist interested in explaining and predicting lion behavior. (cf. PA 641a7-17)”Martha Nussbaum, ed., Aristotle’s De Motu Animalium, Essay 1, (Princeton: Princeton University Press, 1978) p. 71.
The arrangements of parts is what members of a species have in common; it is the reason that they belong to the same species. The substantial form is the cause of this arrangement; and the soul is the substantial form for living things. Aristotle, thus, is not a materialist in that he believes things cannot be reduced to their atomic constitution. Rather, Aristotle appeals to the Formal Cause to account for the reason the material constituents are arranged as they are.
Just as prime matter cannot exist without some substantial form, substantial form is not instantiated (usually) except in some material substrate. That is, for most animals, a soul cannot exist except in a body. Moreover, a soul of a certain kind (of plant or animal) can only enform a body of a certain specific type and arrangement as determined by the kind of living thing (plant or animal) whose soul makes this body to be a living body. Thus, when the body of a plant or an animal ceases to be a living body, the soul ceases to be also. (Summa Theologiae Ia, 75, 3) To suppose that the same soul might exist as a dog, a lion and a human being would be to Aristotle and Aquinas totally incomprehensible; they do not believe in a transmigration of souls. Although the souls of almost all living things cease to exist with the death of the body, the case of the human soul presents Aquinas and Aristotle with certain problems. (Click here to learn about Aquinas’ teaching on the relation of body to soul in general, and the human soul in particular.)
In addition to the causes that are components of material things, matter and form, Aristotle also shows that there must also be a source for any motion or change. This may be external, as in the case of accidental changes that are the result of human artistry; for example, a sculptor is the efficient cause of a statue. The efficient cause of substantial changes are external to the thing that comes to be; parents are the efficient causes of the coming to be of offspring.
The efficient cause of a motion may be also be internal to the thing. In natural motions the efficient cause of the motion is the natural form of the thing that changes. This applies to all the kinds of motions there are, i.e. natural alterations (an apple turning from green to red), the growth of plants and animals, and all natural local motions. This doctrine of natural motions even applies to inanimate bodies since for Aristotle and Aquinas natural bodies tend to their natural place (fire tends up, earth tends down). The internal source for the motion of growth for all living things is soul. Animals have the further motions of local motion and sensation, and the efficient cause of these motions is also soul.
Aquinas uses the notion of efficient cause in various ways in the first three of his five proofs for the existence of God (S.T. Ia, 2, 3). The basic line of reasoning claims that we observe effects that must have been produced by some efficient cause. That cause itself is either caused by something prior, or it is uncaused. Since there cannot be an infinite regress in essentially subordinated causes (i.e. causes that rely on prior causes to exercise their own causality), there must be some First Cause (which Aquinas believes must be God) of all the effects that follow from it. However, Aristotle believes that the world has always been in motion, and Aquinas believes, against the opinion of St. Bonaventure, for example, that there is no way to prove or disprove this belief in the eternity of the world from a philosophical point of view (S.T. Ia, 46, 1). Aquinas, therefore, believes that it is an article of faith that the world had a beginning in time (S.T. Ia, 46, 2). Nevertheless, he still believes that even an eternal world requires an efficient cause to sustain the motions that occur within it, and a world stretching back into an infinite past, nevertheless, leads to the same conclusion that there is a God, who is the First Cause of that infinitely old world.
The problem of the whether the eternity of the world is a philosophically necessary conclusion, and whether its truth implies the non-existence of God, were exceedingly important problems for Aquinas. So much so, that he wrote an entire work on the subject: On the Eternity of the World.
The final cause, according to Aristotle is that for the sake of which motion happens. It is the end or purpose for which the motion takes place. Again, it is easy to understand this doctrine if one considers motions which humans initiate. A sculptor sculpts in order to produce an statue, which he might do in order to make money. In nature, the final cause is not external to the thing that acts, but internal. Fruit does not grow to be food for humans and animals, but for the sake of generating another tree. Thus, typically, in generation, the final cause is the full actualization of the form, i.e. the mature adult of whatever species is generated. This doctrine has received the charge of anthropomorphism. However, for Aristotle, the fact that nature works “always or for the most part” to produce the same result is evidence that there is a genuine cause at work.
The notion of final causality is used by Aquinas as the basis for another proof for the existence of God, i.e. the Fifth Way (S.T. Ia, 2, 3). It should be noted, however, that the proof does NOT say that there is a purpose to the whole universe, and that this ultimate final cause is God (even though Aquinas does believe this). The proof merely asserts that something or other acts for an end which it does not know and does not choose, and that this fact shows that there is a cause of those things which directs them to their final causes. The notion of final cause is also the basis of Thomistic Natural Law.