Abstract

The term “substance” has two main uses in philosophy. Both originate in what is arguably the most influential work of philosophy ever written, Aristotle’s Categories. In its first sense, “substance” refers to those things that are object-like, rather that property-like. For example, an elephant is a substance in this sense, whereas the height or colour of the elephant is not. In its second sense, “substance” refers to the fundamental building blocks of reality. An elephant might count as a substance in this sense. However, this depends on whether we accept the kind of metaphysical theory that treats biological organisms as fundamental. Alternatively, we might judge that the properties of the elephant, or the physical particles that compose it, or entities of some other kind better qualify as substances in this second sense. Since the seventeenth century, a third use of “substance” has gained currency. According to this third use, a substance is something that underlies the properties of an ordinary object and that must be combined with these properties for the object to exist. To avoid confusion, philosophers often substitute the word “substratum” for “substance” when it is used in this third sense. The elephant’s substratum is what remains when you set aside its shape, size, colour, and all its other properties. These philosophical uses of “substance” differ from the everyday use of “substance” as a synonym for “stuff” or “material”. This is not a case of philosophers putting an ordinary word to eccentric use. Rather, “substance” entered modern languages as a philosophical term, and it is the everyday use that has drifted from the philosophical uses.