Early Modern Philosophy

Locke on Substance

(Essay Concerning Human Understanding, Book II, Chapter xxiii)

We have now moved from Locke's account of simple ideas to his account of complex ones. Recall that he wants to identify all the simple ideas, and then explain complex ideas as constructed somehow out of simple ones.

[It's natural to think of the construction of complex ideas out of simple ones as simply a matter of literally combining simple ideas into a bigger complex idea. Frequently Locke does seem to think of it this way. But in fact he suggests that there are many ways of getting complex ideas from simple ones, including comparing, compounding, and abstracting: see II.xi.]

Locke distinguishes between three main kinds of complex ideas: ideas of "mixed modes" (i.e. ideas of compound properties such as that of being red, round, and smooth); ideas of substances (i.e. things); and ideas of relations.

Chapter II.xxiii is about the second of these three kinds of complex ideas, ideas of substances.

Locke begins with the question of how we acquire these ideas. He apparently assumes that all our simple ideas are ideas of qualities (as opposed to things that have qualities). So how do we get the idea of a thing (a ball, or a person, or a tree, or whatever)?

Answer: we notice "that a certain number of these simple ideas go constantly together" (II.xxiii.1). (For instance, if I hold a piece of chalk and wave it around, I notice that my perceptions of whiteness, cylindricality, and inch-long-ness vary together: at first they are clustered on my right, then in the middle of my visual field, then on its left. [Does the idea or perception of solidity also "go with" the visual ideas? It's not entirely clear what "going together" would mean for perceptions associated with different senses.])

All we actually perceive, on Locke's view, are these qualities. But the qualities are "presumed to belong to one thing." Why? "[N]ot imagining how these simple ideas can subsist by themselves, we accustom ourselves, to suppose some substratum, wherein they do subsist, and from which they do result, which therefore we call substance."

So the idea of the chalk seems to be built out of the following ideas: white, cylindrical, inch-long, solid, substance. We get the first four ideas from the senses. But where does the last one come from? Locke thinks that all our ideas come from experience, but he also thinks that there is no such thing as the direct experience of a substance. So where can the idea come from?

Locke doesn't seem to have an answer to this question. Indeed, he seems to come very close to saying that we don't really have such an idea at all.

Quotable quotes (about the obscurity of the idea of substance):

[W]e have no idea of what [substance] is, but only a confused obscure one of what it does (II.xiii.19).

[B]ecause we cannot conceive, how [sensible qualities] should subsist alone, nor one in another, we suppose them existing in, and supported by some common subject; which support we denote by the name substance, though it be certain, we have no clear, or distinct idea of that thing we suppose a support (II.xxiii.4).

. . . the secret and abstract nature of substance in general . . . (II.xxiii.6)

[W]e have as clear a perception, and notion of immaterial substances, as we have of material. . . . For our idea of substance, is equally obscure, or none at all, in both; it is but a supposed, I know not what, to support those ideas, we call accidents. . . . (II.xxiii.16)

Last update: March 5, 2009. 
Curtis Brown  |  Classical Modern Philosophy   |  Philosophy Department  |   Trinity University