Philosophy 100 Heusser SG 7c

Notes on Locke’s Primary/Secondary Quality Distinction(s)

Locke is very obscure on the topic of primary and secondary qualities, but the distinction is crucial if we are to have any possibility of distinguishing the world “out there” (“formal reality” in Descartes) from the world “in here” (“objective reality” in Descartes) within Locke’s system.

The three definitions of the distinction given here can, if I am correct, be found in various attempts by Locke to give what he thinks is one distinction. I suggest focusing on the third distinction. All references are to the Essay Concerning Human Understanding, Bk. II, and Ch. VIII. Each distinction has importance either in its own right or because it was what has often been assumed to be Locke’s intention. (Note: This interpretation of Locke does not have the official sanction of the American Philosophical Association and may be dangerous to your health.)

I. First Distinction (Principal source, Section 9): Primary qualities are those properties a bit of matter cannot lose so long as it exists. By inference, secondary qualities are those properties a bit of matter can lose and still exist.

• Notes: This definition raises the question, “What are the essential qualities a bit of matter must have?” And one can look over the list of primary qualities and secondary qualities given by Locke and ask whether each is or is not essential.

II. Second Distinction (Primary sources, Sections 10 and 23): Secondary qualities are those properties of a bit of matter that are mere powers in it to cause certain kinds of sensations in us. Primary qualities are properties a bit of matter has quite independently of any powers it may have to cause any sensations in us.

• Notes: Keith Donnellan* is inclined to think this comes closest to Locke’s intention. (But he also feels this is a chancy textual interpretation.)

III. Third Distinction (Principal source, Section 15): Primary Qualities are those properties of a bit of matter that resemble the sensations we have when sensing it. Secondary qualities are, as in Distinction 2, mere powers to cause sensations in us, but the sensations have no resemblance to anything in the bit of matter.

• Notes: The 3^rd may sound like the 2^nd but resemblance plays no part in the other distinctions. This seems to be the only one that has relevance to the question of how we can penetrate our sensations and learn about the external spatial world, the world Berkeley believes to be a philosopher’s myth.
• Many of the experiments, as I will call them, which Locke uses to show, he thinks, that certain qualities are secondary (and which Berkeley argues can just as well go through for all qualities) seem to presuppose that this third distinction is the one to be established.

*Much of this handout courtesy of Keith Donnellan, U.C.L.A. Any mistakes are my own.