David Wörner

The identity of indiscernibles states that indiscernible objects must be identical. Many philosophers have held that the PII turns out to be either true but trivial, or non-trivial but false, depending on how the notion of discernibility is spelled out. In this paper, I propose and defend an account of this notion which aims to yield a minimally non-trivial and yet plausible version of the PII. I argue moreover that this version of the principle is immune to a number of well-known and recent objections to the PII.

John Locke famously claimed that our idea of substance is but a confused idea of “something we know not what.” However, he also thought that the idea of substance is a fundamental part of our ideas of ourselves and the objects surrounding us—of objects we do know. Interpreting this apparently ambivalent stance has long been a major challenge for Locke scholarship. In this article, I argue that the leading interpretations of Locke's conception of substance have failed to resolve this tension because they have misconstrued the source of Locke's skepticism about our knowledge of what substance is. This skepticism, I argue, issues from an observation about the signification of the term “substance”: Locke maintained that the philosophical usage of the term is irremediably equivocal. This reading allows us to acknowledge that Locke could consistently hold that ordinary objects, such as persons, horses, or trees, are paradigmatic examples of substances. It also points to a better appreciation of how Locke's discussion of substance relates to the scholastic conceptions of substance he tried to overcome.

In this paper I examine Locke’s criticism of the view that some species of natural objects are determined by real essences, a view I call species realism. Most commentators have focused either on Locke’s putative objections to the realist’s claim that species determining real essences exist or on his semantic case against the assumption that our species terms can refer to real essences that determine species. I identify another objection, which, I argue, is independent from both of these lines of criticism. This objection is essentially practical. It is based on the claim that adopting species realism has detrimental practical consequences: it undermines, Locke believes, our ability to sort particular natural objects into species. This alone, he argues, is already sufficient to set aside and ignore species realism when trying to sort objects into species.