Overview

How do our ideas correspond to external objects? There is a naive view of perception that we directly perceive the qualities that objects have. Locke dissents. But secondary qualities, like colors, sounds, tastes, and heat are qualities of our perceptions rather than of objects.

Locke also raises some questions about substance. We think that there are things underlying the qualities that we perceive. The things have the qualities. What is there other than the qualities? Substances! But since all we have are ideas of qualities, we do not have know what substances are.

Primary and Secondary Qualities

First, we need a distinction between ideas and qualities.

An idea is “whatever the mind perceives in itself or is the immediate object of perception, thought, or understanding” while a quality is, “the power to produce any idea in our mind” (Locke [1690] 2019, 363L). For examples, a snowball can produce the ideas of white, cold, and round. The powers to produce these ideas are qualities of the snowball. Ordinarily, you would say that the snowball is cold, white and round. But the way Locke has it, the snowball has the power to produce the ideas of cold, white, and round.

Primary qualities are,

such as are utterly inseparable from the body in whatever state it is, such as in all the alterations and changes is suffers, all the force can be used upon it, it constantly keeps, and such as sense constantly finds in every particle of matter which has bulk enough to be perceived, and the mind finds inseparable from every particle of matter, though less than to make itself singly be perceived by our senses. (Locke [1690] 2019, 363L)

For example, divide a grain of wheat over and over. The parts will always have solidity, extension, figure, and mobility (§9). In subsequent sections, he adds bulk, texture, motion (which might be another way of saying “mobility”) (§10) and number, situation, and motion, or rest of solid parts (§23).

Secondary qualities are “such qualities which in truth are nothing in the objects themselves but power to produce various sensations in us by their primary qualities” (Locke [1690] 2019, 363R). These include “colors, sounds, tastes, etc.”

Our ideas of primary qualities resemble objects as they really are; they would have those properties even if we did not exist. But our ideas of secondary qualities do not resemble the way objects really are. If we were not around to perceive the table, it would not have any color.

Locke’s arguments for the unreality of secondary qualities are found in sections 19-21 (Locke [1690] 2019, 365).

• The colors in porphyry (a rock with crystals) vanish when you turn off the light, but that does not alter the rock (§19)

• Almonds look and taste different when pulverized, suggesting that color and taste depend on the primary quality of the almond’s texture (§20)

• One bucket of water can feel warm to one hand and cold to another (§21)

Substances

Locke thinks that substances are things that have observable qualities. The pencil, for example, is extended, yellow, hexagonal, pointy, and so on. When we say something like that, we don’t mean that a pencil is identical with a list of qualities. We mean that there is a thing that has the qualities: the pencil.

But we never directly perceive this thing since all we get from experience are the qualities. A comparison with Descartes’s discussion of how reason tells him the essential features of a ball of wax would be apt here, I think.

So where do we get the idea of substances? Locke thinks we notice that some simple ideas go constantly together and we assume they belong to one thing. The simple ideas cannot exist by themselves, so we suppose there is a “substratum” in which they subsist. That is the substance. We have no idea of substance other than that we “know not what” supports the qualities that go together (Locke [1690] 2019, 389R).

Given the obscurity of substances, Locke expresses some doubts about the problem of mind-body interaction that plagued poor Descartes. For example, one way we identify mental substance is that it is a thing that thinks. But we also identify it as a thing that moves the body. The second idea is no more obscure than the first, so there is no special problem of how the mind interacts with the physical world (Locke [1690] 2019, 394).

I do not know if Princess Elisabeth would have found that satisfying.