Primary and Secondary Qualities

II.viii is intended as a further discussion of simple ideas. Locke draws what should by now be a familiar distinction. Can you reconstruct Locke’s argument?

(From II.viii.7—Ideas in the Mind, Qualities in Bodies) To discover the nature of our ideas the better, and to, discourse of them intelligibly, it will be convenient to distinguish them as they are ideas or perceptions in our minds; and as they are modifications of matter in the bodies that cause such perceptions in us …

(From II.viii.8—Our Ideas and the Qualities of Bodies) Whatsoever the mind perceives in itself, or is the immediate object of perception, thought, or understanding, that I call idea; and the power to produce any idea in our mind, I call quality of the subject wherein that power is. Thus a snowball having the power to produce in us the ideas of white, cold, and round—the power to produce those ideas in us, as they are in the snowball, I call qualities; and as they are sensations or perceptions in our understandings, I call them ideas; which ideas, if I speak of sometimes as in the things themselves, I would be understood to mean those qualities in the objects which produce them in us.

(From II.viii.9—Primary Qualities of Bodies) Concerning these qualities, we, I think, observe these primary ones in bodies that produce simple ideas in us, viz. solidity, extension, motion or rest, nubmeror figure. These, which I call original or primary qualities of body, are wholly inseparable from it; and such as in all the alterations and changes it 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, thoughless than to make itself singly be perceived by our senses: e.g., take a grain of wheat, divide it into two parts; each part has still solidity, extension, figure, and mobility: divide it again, and it retains still the same qualities …

(From II.viii.11—How Bodies produce Ideas in us) The next thing to be considered is, how bodies operate one upon another; and that is manifestly by impulse, and nothing else. It being impossible to conceive that body should operate on what it does not touch (which is all one as to imagine it can operate where it is not), or when it does touch, operate any other way than by motion.

(From II.viii.13—How secondary Qualities produce their ideas) After the same manner that the ideas of these original qualities are produced in us, we may conceive that the ideas of secondary qualities are also produced, viz. By the operation of insensible particles on our senses. … [L]et us suppose at present that, the different motions and figures, bulk and number, of such particles, affecting the several organs of our senses, produce in us those different sensations which we have from the colours and smells of bodies … It being no more impossible to conceive that god should annex such ideas to such motions, with which they have no similitude, than that he should annex the idea of pain to the motion of a piece of steel dividing our flesh, with which that idea hath no resemblance.

(From II.viii.14—They depend on the primary Qualities ) What I have said concerning colours and smells may be understood also of tastes and sounds, and other the like sensible qualities; which, whatever reality we by mistake attribute to them, are in truth nothing in the objects themselves, but powers to produce various sensations in us; and depend on those primary qualities, viz. Bulk, figure, texture, and motion of parts and therefore I call them secondary qualities.

(From II.viii.15—Ideas of primary Qualities are Resemblances; of secondary, not) From whence I think it easy to draw this observation, that the ideas of primary qualities of bodies are resemblances of them, and their patterns do really exist in the bodies themselves, but the ideas produced in us by these secondary qualities have no resemblance of them at all. There is nothing like our ideas, existing in the bodies themselves. They are, in the bodies we denominate from them, only a power to produce those sensations in us …

(From II.viii.17—The ideas of the Primary alone really exist ) The particular bulk, number, figure, and motion of the parts of fire or snow are really in them, whether any one’s senses perceive them or no: and therefore they may be called real qualities, because they really exist in those bodies. But light, heat, whiteness, or coldness, are no more really in them than sickness or pain is in manna. Take away the sensation of them; let not the eyes see light or colours, nor the can hear sounds; let the palate not taste, nor the nose smell, and all colours, tastes, odours, and sounds, as they aresuch particular ideas, vanish and cease, and are reduced to their causes, i.e., bulk, figure, and motion of parts.

(From II.viii.19—Examples) Let us consider the red and white colours in porphyry. Hinder light from striking on it, and its colours vanish; it no longer produces any such ideas in us: upon the return of light it produces these appearances on us again. Can any one think any real alterations are made in the porphyry by the presence or absence of light; and that those ideas of whiteness and redness are really in porphyry in the light, when it is plain it has no colour in thedark? It has, indeed, such a configuration of particles, both night and day, as are apt, by the rays of light rebounding from some parts of that hard stone, to produce in us the idea of redness, and from others the idea of whiteness; but whiteness or redness are not in it at any time, but such a texture that hath the power to produce such a sensation in us.

(From II.viii.20) Pound an almond, and the clear white colour will be altered into a dirty one, and the sweet taste into an oily one. What real alteration can the beating of the pestle make in an body, but an alteration of the texture of it?

(From II.viii.21—Explains how water felt as cold by one hand may be warm to the other) Ideas being thus distinguished and understood, we may be able to give an account how the same water, at the same time, may produce the idea of cold by one hand and of heat by the other: whereas it is impossible that the same water, if those ideas were really in it, should at the same time be both hot and cold. For, if we imagine warmth, as it is in our hands, to be nothing but a certain sort and degree of motion in the minute particles of our nerves or animal spirits, we may understand how it is possible that the same water may, at the same time, produce the sensations of heat in one hand and cold in the other; which yet figure never does, that never producing the idea of a square by one hand which has produced the idea of a globe by another.

Locke argues for three theses in this chapter:

If there were no observers or perceivers, what would the world be like, according to Locke? That is, what qualities does a physical object have in itself?

How does Locke argue for his three theses? Let’s start with (i): ideas of secondary qualities resemble nothing in the objects.

Recall Aquinas’s picture of (bodily) causation: one object (e.g., fire) produces in another the same kind of quality it has in itself (e.g., heat). Why does Locke think that there isn’t really any heat in the first object? Let’s take a case where fire produces a sensation of heat in a person. If our sensation of heat resembled any quality in the object, that quality would have to be the cause of the heat that it produces.

Why think that the color of an object (i.e., the color ideas it produces in us) depends on its primary qualities?

(Hint: use II.viii.20)

Finally, what about thesis (iii): secondary qualities are nothing but powers in objects to produce certain ideas in us? Well, this is just to combine (i) and (ii). If they’re not resemblances, and they depend on the primary qualities, then to say that a body has a particular color is just to say that its parts are so arranged as to produce a given idea in us. (Note that primary qualities are powers and genuine qualities in objects; secondary are merely powers.)

But as Locke points out, ideas of secondary qualities depend not just on the objects; they also depend on the perceivers.