Reid on the Real Foundation of the Primary–Secondary Quality Distinction

Abstract

What is the basis of the distinction between primary and secondary qualities? Is it that primary qualities reside in external objects and secondary qualities in the mind only? Reid says no. Is it that primary qualities resemble ideas in our minds and secondary qualities do not? Reid again says no. Positively, he says we have a direct conception of primary qualities and only a relative conception of secondary qualities as powers to cause certain sensations. Is his own way of drawing the distinction then merely epistemological? This chapter says no: for Reid there is a distinction in the nature of the properties themselves, primary qualities being intrinsic and secondary qualities extrinsic. Relatedly, secondary qualities for Reid are better thought of as dispositions than as causal bases of dispositions. Finally, the chapter brings out the significance of Reid's views by calling attention to four other views that are wrong if he is right.