ABSTRACT
What is wrong with Locke's account of the names of substances? Although he allowed that where the observable attributes constituting the nominal essence of, say, 'water' recur, some underlying structure will reasonably be supposed also to recur, he nevertheless insisted that that supposition is semantically inert. For this he gave, broadly speaking, two reasons. First, it is impossible that our employment of the term should be determined by what is unknown to us; and, second, the supposition of a real essence can supply no boundary to the species other than the boundary supplied by a nominal essence, i.e. an arbitrary definition. These reasons may be connected, but they raise rather different issues.
