Reading: Understanding Form and Matter

Aristotle introduces his notions of matter and form in the first book of his Physics, his work on natural science. Natural science is concerned with things that change, and Aristotle divides changes into two main types: there are accidental changes, which involve concrete particulars, or “substances” (ousiai) in Aristotle’s terminology, gaining or losing a property (see Categories 1–5, Physics i 7). For instance, the changes whereby Socrates falls in a vat of dye and turns blue, or puts on a few pounds from excessive feasting during the Panathenaia, count as accidental changes (in the categories of quality and quantity, respectively). Socrates, a substance, gains the property of being blue, or the property of weighing twelve stone. The other main kind of change is substantial change, whereby a substance comes into, or passes out of, existence. For example, when Socrates dies [...] a substantial change has taken place.

Matter and form are required to account for this second kind of change, if it is to conform to Aristotle’s general conceptual analysis of change. In any change, he contends, there must be three things: (1) something which underlies and persists through the change; (2) a “lack”, which is one of a pair of opposites, the other of which is (3) a form acquired during the course of the change (Physics i 7, 190a13–191a22). Thus, for example, in an accidental change, the underlying thing is the substance which acquires a new accidental property. For instance, when Socrates learns to play the flute, he transitions from a state of being unmusical (the lack) to a state of musicality (the form). But for us to be able to say that there is something which has changed, there must be something which remains the same throughout the change, and in this case the obvious candidate is Socrates, who is one and the same person throughout his musical training.

In accidental changes there is always a substance to underlie the change, but this is not true for substantial changes, since these involve the coming to be or passing away of a substance (see the amusing remark of Irving Copi, quoted at the start of the entry on identity over time). In these cases, the thing that underlies is the matter of the substance. When someone builds a house, it is the bricks which persist through the change. They transition from a state of not being a house to acquire the property of being a house. Aristotle often uses the example of artefacts like houses, even though he does not regard them as substances properly-speaking (Metaphysics vii 17, 1041b28–30), because their matter is more straightforward to identify. Nevertheless, the same analysis holds in the case of organisms, which are the substances proper: when an organism is created or destroyed, when an acorn becomes an oak tree, or a human dies, there must be some matter which persists through the change. To say otherwise would be to say that things can come to be out of, or vanish into, nothing, and Aristotle understandably agrees with his predecessor Parmenides that this is impossible (Physics i 8, 191a23–b17). Aristotle’s metaphysics takes as its starting points observed phenomena, and seeks to preserve common sense beliefs where possible. We never experience anything simply appearing or disappearing at random.

The word “form” may misleadingly suggest that what is acquired in a case of substantial generation is simply a shape, and this impression is reinforced by some of the examples that Aristotle uses, especially when focusing on artefacts: plausibly the form of a bronze statue just is its shape. When we consider organisms, however, it becomes apparent that having the right shape is not sufficient to possess the form. A thing’s form is its definition or essence—what it is to be a human being, for example. A statue may be human-shaped, but it is not a human, because it cannot perform the functions characteristic of humans: thinking, perceiving, moving, desiring, eating and growing, etc. The connection between a thing’s form and its function emerges in Physics ii 3, where Aristotle distinguishes his four kinds of cause: material, formal, efficient, and final, and suggests a special connection between the formal and final cause.

Here one needs to proceed cautiously, however, since it is sometimes said that Aristotle’s word “cause” (aitia) would be better translated as “explanation” (or “explanatory factor”, to avoid the implication that they are linguistic items, as opposed to things-in-the-world). Certainly modern philosophers tend to use “cause” in a narrower way, which approximates to Aristotle’s efficient cause. Aristotle’s idea is that there are four kinds of thing that need to be mentioned in order to give a full account of the nature of an object, each corresponding to a particular kind of question. We need to know what the thing is made of, and the answer to this question is the thing’s matter—bricks, in the case of a house; bodily organs in the case of a human being. Next we need to know what the thing is, or how it is defined, and the answer to this is the thing’s form or essence. We also need to know what made the thing come into existence, who or what created it, and this is the thing’s efficient or “moving” cause. Lastly, we need to know what the thing is for, what its purpose or function is—the final cause. Now Aristotle observes that, although these are all distinct questions, in the case of the last three very often the same thing will serve as the answer to all of them (Physics ii 7, 198a24–27). A house is defined as a shelter of a certain sort (De Anima i 1, 403b3–7; Metaphysics viii 3, 1043a29–36). That is what a house is, i.e., its formal cause, but it is also what a house is for, its final cause, since houses, like all artefacts are functionally defined. Similarly, a human being is defined as something which lives a certain kind of rationally-directed life. But, on Aristotle’s view, this is also what a human being is for. The human function is to live such a life (Nicomachean Ethics i 7, 1097b22–1098a20; cf. De Animaii 1, 412a6–22). As for the efficient cause, it is qualitatively, although not numerically, identical with the formal cause, at least in the organism case, since human beings give birth to human beings, and the same goes for all other living things. Thus, even though Aristotle admits four different kinds of cause, in a sense it is only really matter and form that play any ineliminable explanatory role in his system.

In fact, Aristotle does not simply focus on the case of artefacts because their pre-existing matter is easier to identify. There is a particular issue here with the case of organisms, which arises out of Aristotle’s insistence that a human being, for instance, is composed of a rational soul, which is the form, and an organic body, which is the matter (for further discussion of this problem, see Ackrill 1972/73). It is characteristic of the matter of artefacts that numerically the same stuff which makes up one object can later be used as the matter of another: for instance, when one melts down a bronze statue, and then molds it into some jewelry, it is the same bit of bronze throughout. It is crucial that a thing’s matter can survive such changes, if it is to play the role that Aristotle needs it to play in cases of substantial generation and destruction, as being the thing that underlies such changes. If an artefact’s matter only contingently has the form it has, the same does not obviously seem true of organisms. Unlike in the case of a house built from bricks, it does not seem as though one’s body predates one’s existence, and so can serve as the underlying thing in a case of substantial generation. One might think that at least the body does exist after death, but in fact Aristotle would disagree. Instead, he insists that a dead body is only “homonymously” called a body—that it is only described as “a body” by extension, because it superficially resembles a living body (De Anima ii 1, 412b10–25; Metaphysics vii 10, 1035b9–25). It is not a real body, because it is incapable of performing the functions normally associated with bodies, just as a statue’s eye, or an eye in a painting, is not a real eye, because it is made of stone or paint, and thus cannot serve the function that genuine eyes exist for—seeing.

It might seem that Aristotle is rather going against ordinary linguistic usage here, since we in fact regularly do refer to dead bodies as “bodies”. Whether a dead body is really a body might seem like a trivial linguistic issue, which can simply be decided by fiat. The obvious way to resolve the problem might seem to be simply to drop the insistence that the body cannot exist without being coupled to a living human soul. Allowing that a dead body remains the same body as its living counterpart will not help the difficulty of what to say about the matter that predates the coming to be of the organism, when there is no apparent body, living or dead. What is more, Aristotle is deeply committed to his position that the human body is essentially ensouled, because of his view that things are defined by their functions (Meteorologica iv 12, 390a10–15; Generation of Animals ii 1,734b24–31). It seems as though he believes that a human being’s matter must be contingently alive, so that it can serve as the underlying thing that remains when the human being comes into existence, but also that it must be essentially alive, because it is functionally defined. If so, he contradicts himself. 

The best way to resolve this apparent contradiction in Aristotle’s hylomorphism is to point out that an organism can have more than one level of matter. Aristotle believes that all sensible substances can be analyzed into matter and form, but such an analysis is not restricted to the things he calls substances. Matter can itself be divided into matter and form: for instance, bricks are made of clay, shaped into cuboid blocks. Again, clay has its own matter—mud, say—and so on. Eventually, if one pursues this hierarchy of matter far enough downwards, Aristotle believes that one will reach the four elements, earth, air, fire and water. He agrees with Empedocles that everything in the sub-lunar world is ultimately made up of different ratios of these four elements. Matter then should really be understood as a relative notion—it is always the matter ofsomething. Aristotle distinguishes between a thing’s proximate matter, the stuff it is most immediately made of, and its less proximate matter, i.e., the matter of its matter, or even further down the hierarchy, culminating in its ultimate matter, the elements. The organic body which is a human being’s proximate matter is essentially alive, but this need not apply to all of the other matter further down the chain. Aristotle distinguishes between homoiomerous and heteromerous parts (Parts of Animals i 1, 640b25–30). Homoiomerous parts are stuffs, like bronze or flesh, which Aristotle believes have no internal structure. Every part of a homoiomerous stuff is the same as every other part, containing the same ratio of elements. This view of homoiomerous parts is consistent with Aristotle’s denial of atomism; he believes that matter, as well as space and time, are infinitely divisible. The bodily organs, hands, feet, eyes, hearts, etc., are heteromerous, since they do have internal structure, with different parts of them made up of different stuffs. A person’s hand, for instance, is made of flesh, bones, blood and other such biological matter, which in turn are made of earth, air, fire and water. It may be that flesh too is functionally defined, so that dead flesh is only called “flesh” homonymously as well. Even if nothing biological can exist when not alive, it seems clear that the elements at least must be able to do so. Therefore there will be some, low-level matter to serve as the thing that underlies the coming to be and passing away of organisms, even though an organism’s proximate matter exists for precisely as long as it does.