Traditionally, this puzzle has been solved in various ways. Aristotle, for example, distinguished between “accidental” and “essential” changes. Accidental changes are ones that don't result in a change in an objects' identity after the change, such as when a house is painted, or one's hair turns gray, etc. Aristotle thought of these as changes in the accidental properties of a thing. Essential changes, by contrast, are those which don't preserve the identity of the object when it changes, such as when (...) a house burns to the ground and becomes ashes, or when someone dies. Armed with these distinctions, Aristotle would then say that, in the case of accidental changes, (1) and (2) are both false—a changing thing can really change one of its “accidental properties” and yet literally remain one and the same thing before and after the change. (shrink)

In this paper, I consider the validity and proper formulation of the only-x-and-y principle, which states, roughly, that whether a later individual, y, is numerically identical to an earlier individual, x, can depend only on facts about x and y and the relationships between them. In the course of my investigation, I distinguish between two classes of physical entities - those that exist in a 'real' sense, and those that exist in a mere Cambridge sense. This distinction is grounded in (...) Peter Geach's distinction between 'real' and mere Cambridge change. I argue in favor of a modified version of the only-x-and-y principle - the qualified only-x-and-y principle - which applies to entities that exist in a 'real' sense, but not to mere Cambridge entities. It is also argued that the plausibility of the qualified only-x-and-y principle has more to do with facts about the nature of causality than with intuitions we have about existence or numerical identity. I finish by considering some traditional objections to the only-x-and-y principle, and conclude that they do not succeed in refuting the qualified only-x-and-y principle. (shrink)

This note criticizes Andrew Brennan's attempt to defend best?candidate theories of the identity of artefacts over time against certain now familiar objections. Adoption of a mereological conception of individuals does not, in itself, provide the means for a satisfactory response to objections of Wiggins and Noonan (some of which are anyway ill?focused). The way forward consists in recognizing that the consequences of best?candidate theories which have been thought objectionable (in particular, commitment to the extrinsicness of identity) do not violate the (...) necessity of identity and imply ? what anyway ought to seem unexceptionable ? that a predicate such as ?constituting the ship which is the Ship of Theseus? does not denote a genuine property of the hunk of matter of which the predicate is true. Once these consequences have been clearly mapped out, the best?candidate theorist's commitment to the extrinsicness of identity does not appear absurd. (shrink)