This is the second edition of an award-winning 1981 book (Princeton University Press and Basil Blackwell, based on the author’s doctoral dissertation) considered to be a classic in the philosophy of language movement known variously as the New Theory of Reference or the Direct-Reference Theory, as well as in the metaphysics of modal essentialism that is related to this philosophy of language.

The paper defends Gareth Evan's argument against vague identity "de re" from a criticism that quantum mechanics provides actual counter-examples to its validity. A more general version of Evans's argument is stated in which identity involving properties are not essential and it is claimed that the scientific facts as so far known are consistent with the Evansian thesis that indeterminacy in truth-value must always be due to semantic indecision.

Lowe has recently argued that quantum particles offer examples of vague objects. While accepting the premise of the argument that such particles can be regarded as individuals, we point out that there is a lacuna here, to be filled by a detailed analysis of the nature of the entangled states which they enter into. We then elaborate the alternative view, according to which such particles should be regarded as non- individuals' and situate it in the context of recent developments of (...) a logic of non- individuality. Our conclusion is that it is here that one encounters genuine ontic vagueness. (shrink)