Matter and Form

Aquinas thinks that some things are made out of matter and other things (such as angels) are not. It is easiest to approach his theory of things by beginning with his views about things made out of matter. A macro-level material thing is matter organized or configured in some way, where the organization or configuration is dynamic rather than static. That is, the organization of the matter includes causal relations among the material components of the thing as well as such static features as shape and spatial location. This dynamic configuration or organization is what Aquinas calls ‘form’. A thing has the properties it has, including its causal powers, in virtue of having the configuration it does; the proper operations and functions of a thing derive from its form. (I am here thus making a conceptual distinction between the organization of a thing and the properties the thing has in virtue of being organized in that way, and in what follows I will sometimes speak of a form’s conferring certain properties on the whole it configures.)

Like many contemporary philosophers, Aquinas recognizes levels of organization. What counts as matter for a macro-level object may itself be organized or configured in a certain way; that is, the matter of a thing may itself be constituted of matter and form.

A typical medieval example given to illustrate the matter/form distinction is a bronze statue, but for our purposes here it will be more helpful to take a contemporary example. So consider the protein called ‘CAT/Enhancer-Binding Protein’ (C/EBP), one of the proteins known to play an important role in regulating gene expression. In its active form, the molecule is a dimer with an alpha helix coil. On Aquinas’s way of thinking about material objects, the form of C/EBP is the configuration of the dimer, including the alpha helix coil; and the dimer subunits constitute the matter. Of course each dimer subunit is itself a composite. The form of the subunit is the configuration of its amino acids, in which, for example, in one region every seventh spot must be occupied by leucine; and the amino acids composing the subunit are its matter. Amino acids themselves are also clearly composites, however. The matter of an amino acid such as leucine is the carbon, hydrogen, nitrogen and oxygen of which it is composed, and the form is the way that material is combined, including the characteristic NH2 configuration common to all the amino acids and the sequence of carbon and hydrogen peculiar to leucine. We can evidently go on in this way until we come, for example, to the proton of a hydrogen atom. The quarks that compose it are its matter, and their configuration — the right combination of and interactions between up and down quarks — is the form of the proton. But at some point this process of moving down the levels of organization of a macro-level thing must come to a halt. For Aquinas, the lowest-level material component which counts as matter organized in a certain way is an element. An element is constituted of matter and form, but if we conceptually strip away the form or configuration of an element, all that remains is prime matter; matter which cannot itself be decomposed further into matter and form.

Prime matter is thus matter without any form at all, “materiality” (as it were) apart from configuration. When it is a component in a matter-form composite, prime matter is the component of the configured composite which makes it the case that the configured thing can be extended in three dimensions and can occupy a particular place at a particular time. But by itself, apart from form, prime matter exists just potentially; it exists in actuality only as an ingredient in something configured. So we can remove form from prime matter only in thought; everything which exists in reality is configured in some way. For this reason, Aquinas sometimes says that form is the actuality of anything. Configuration or organization is necessary for the existence of anything at all; without form, nothing is actual.

This point holds also for immaterial things. For Aquinas, there are things that exist and are organized in a certain way, but the organization is not an organization of matter. An angel, a certain kind of intelligence, is an example. An angel has no matter to configure, but it is nonetheless configured in a certain way. It has certain properties, such as being a knower, and not others, such as weighing two hundred pounds. And so there is a kind of organization in an angel, too, which we can think of as an organization of properties. An angel has one constellation of properties rather than another, and in virtue of these properties it also has one set of causal powers rather than another.

Consequently, although matter is not necessary for the existence of a thing, on Aquinas’s view, form is. For Aquinas, to be is to be configured.

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Eleonore Stump, Aquinas (New York: Routledge, 2003), 36-37.