Locke on the Propria of Body

Seth Pringle-Pattison (233n1) observed that Locke " teaches a twofold mystery—in the first place, of the essence ('for the powers or qualities that are observable by us are not the real essence of that substance, but depend upon it or flow from it'), and in the second place, of the substance itself ('Besides, a man has no idea of substance in general, nor knows what substance is in itself.' Bk. II.31.13). " In this paper, I'll explain the relation between the two mysteries. Our Rosetta Stone is Locke's argument that we understand body and spirit equally well since we are ignorant of their underlying substances but we " have distinct clear Ideas of two primary Qualities, or Properties " (2.23.30) of each. I'll show that he is working with a restricted notion of primary quality in this passage, but one that demonstrably falls under the kind defined in his chapter on primary and secondary qualities. According to Locke, the fundamental primary qualities of bodies flow from corporeal substances and the determinations of these fundamental qualities constitute real essences. Locke's discussion can't be understood without understanding the relevant scholastic background. In the first half of my paper, I'll explain his argument as an idiosyncratic