 Although Locke’s Essay Concerning Human Understanding (1689–90) (hereafter Essay or E, cited by Book, Chapter, and Section number) contains the canonical distinction, it is an inquiry into the origin, limits and sufficiency of human cognition. It is not meant to contribute to theoretical natural philosophy, but to expose abuses of language that hamper it (E [1975: 9–10]). Locke’s attitude toward CT is mixed: he points to its failure to account for the cohesion of the parts of matter and communication of motion (E 2.23.26, 28) but holds it up as the hypothesis that “goes farthest in an intelligible Explanation of the Qualities of Bodies”, (E 2.23; 4.3.12–13).