Abstract

My dissertation is an explication of Locke's influential discussion of primary and secondary qualities. I explain the various distinctions that he draws and the reasons that he offers for his various theses, including the famous thesis that secondary qualities are merely powers to produce ideas in us. ;I begin with machinery. Seventeenth century locksmiths and watchmakers appealed to primary qualities to explain the workings of their machine. Locke treats this mechanical reasoning as a model of how to think about the material world. I begin by explaining how he thinks this sort of reasoning works, how far he thinks it can be trusted, and why he thinks that it explains most phenomena. ;On the basis of these commitments, Locke adopts a corpuscularian theory of perception. I show how this theory and his philosophy of mind leads him to conclude that bodies do not resemble ideas with respect to secondary qualities. I defend the unpopular yet natural interpretation that an idea resembles a quality in a body when the idea is a component of an image that shares some feature with the body. Since Locke wants to preserve the truth of ordinary judgments about secondary qualities, he concludes that bodies possess these qualities in the derivative sense in which apples are called healthy. Bodies are red, loud, or warm only insofar as they produce the ideas that are the paradigms of redness, loudness, and warmth. ;Since he believes that secondary qualities are merely powers to produce ideas in us, Locke belittles secondary qualities metaphysically. I explain why he believes that, unlike primary qualities, secondary qualities are separated from a body by pulverizing it into microscopic bits and why he thinks bodies would have no secondary qualities if there were no perceivers. In my final chapter, I explain what he means when he says that the colors of porphyry change without any real alteration in the stone, and how he rightly infers from this proposition that the colors in porphyry are not real entities and do not belong to porphyry as it is in itself