Primary and Secondary Qualities in Locke

In Book II chapter viii of the Essay Locke provides two related criteria by which primary qualities are to be distinguished from secondary qualities: first, primary qualities are inseparable from the bodies in which they inhere, whereas secondary qualities are not. Second, secondary qualities are merely the observable effects of primary qualities and not real in the same sense in which primary qualities are, indicating an ontological dependence of the former on the latter. Locke uses these two criteria of demarcation to argue to a conclusion about our ideas of primary and secondary qualities, namely that ideas of primary qualities resemble those qualities but our ideas of secondary qualities do not. I will argue here that Locke’s two criteria are flawed and that he is inconsistent in applying them to qualities, and that his mistakes in correctly drawing the ontological distinctions between primary and secondary qualities result in his misapplication of those distinctions to the epistemological realm.

Uneasiness and Desire in Locke

The relation between uneasiness and desire in the chapter on power in the Essay (chapter XXI of book II) is at first glance unclear. The reader is told at one point that desire is uneasiness (II.xxi.32, 251 in the Nidditch edition), but at another the implication is that the instead of being the same thing as uneasiness, instead desire is what causes uneasiness (II.xxi.46, 262). Resolution of this tension is important to understanding Locke’s theory of the will, since uneasiness is taken to be the immediate cause of the will producing action (II.xxi.29, 249, II.xxi.31, 251). I will attempt here to explicate Locke’s concepts of uneasiness and desire in such a way as to highlight this tension in his theory, and will offer a speculation as to the theoretical motivation which may have prompted Locke to offer the account in such a way as to make it susceptible to this tension in the first place. But I don't have a solution on his behalf.