Although the importance, both historically and systematically, of the seventeenth century distinction between primary and secondary qualities is commonly recognised, there is no consensus on its exact nature. Apparently, one of the main difficulties in its interpretation is to tell the constitutive from the argumentative elements. In this paper, we focus on the primary-secondary quality distinctions drawn by Boyle and Locke. We criticise, more specifically, MacIntosh’s analysis of them. On the one hand, MacIntosh attributes too many different primary-secondary quality distinctions (...) to Boyle and Locke. On the other hand, he forbears to attribute a particular primary-secondary quality distinction to them, which, at least in the case of Boyle, differs genuinely from his main distinction between the mechanical affections of matter and all of matter’s other qualities. (shrink)