Abstract

The claim that sensible qualities are sensations, whereas, shape, size and motion are actual features of objects is called "the primary-secondary quality distinction." The goal of this dissertation is to understand the nature of and the arguments for this distinction in the works of Rene Descartes and John Locke. ;With regard to the nature of the distinction, there are two main interpretations. According to one, sensible qualities are ideas, whereas mechanical ones are actual features of objects. According to the other interpretation, Locke and Descartes distinguish between sensible qualities as perceived and as they are dispositions of objects. Sensible qualities are then distinguished from mechanical qualities insofar as the ideas of the former are not resemblances of features of objects, and insofar as sensible qualities as they are in objects are dispositional, not intrinsic, features. ;I argue that the first interpretation is basically correct. Locke's account, however, is complicated by his usage of the "primary-secondary" terminology. These terms were used previously by Robert Boyle, who commentators take to be Locke's source for both the terms and their meaning. I show that what Boyle takes to be primary and secondary qualities are not what Locke takes them to be. The failure to see this has led to the mistaken dispositional account of secondary qualities. Boyle and Locke, however, do agree about which features of our sensory experience are features objects have in themselves. ;With regard to the argument for the primary-secondary quality distinction, some have claimed that the distinction is justified, either directly or through a principle of economy, by the mechanical explanations of phenomena, whereas others have held that it was justified by a priori reflection on our concepts of color, sound and other such qualities. I show that both interpretations are incorrect. Rather, Descartes and Locke use the philosophical assumptions that if sensible qualities existed in objects they would be distinct from the mechanical features, and that if a quality was an object of perception, then it would be the cause of our perceiving it