Abstract

In Book 2, chapter 8, of John Locke’s magnum opus, the Essay Concerning Human Understanding, he formulates perhaps the most famous and influential version of the distinction between primary and secondary qualities. (It is also the first version to use the terminology of primary and secondary qualities. Important early-modern precedents include Galileo, Descartes and Boyle.) Before one can begin an attempt to analyze Locke’s distinction between primary and secondary qualities, one must confront the question: which distinction? The difficulty is that there seem to be at least three primary/secondary-quality distinctions in play in the Essay, including a metaphysical distinction, an epistemological distinction, and a physical/scientific distinction. Our first task, then, is to characterize these three distinctions and, then, to consider their relations.