J. L. Mackie's famous claim that Locke ‘anticipates’ Kripke's Causal Theory of Reference (CTR) rests, I suggest, upon a pair of important misunderstandings. Contra Mackie, as well as the more recent accounts of Paul Guyer and Michael Ayers, Lockean Real Essences consist of those features of an entity from which all of its experienceable properties can be logically deduced; thus a substantival Real Essence consists of features of a Real Constitution plus logically necessary objective connections between them and features of some particular Nominal Essence. Furthermore, what Locke actually anticipates is the most significant contemporary challenge to the CTR: the qua-problem.