Alan Sidelle

I offer an understanding of what it is for a term to be rigid which makes no serious metaphysical commitments to or about identity across possible worlds. What makes a term rigid is not that it 'refers to the same object(property) with respect to all worlds' - rather (roughly) it is that the criteria of application for the term with respect to other worlds, when combined with the criteria of identity associated with the term, ensure that whatever meets the criteria of identity also meets the criteria of application and vice versa - in the simplest case, the criteria of application just are the criteria of identity - but things can be more complex to allow for the necessary a posteriori. This makes rigidity a non-metaphysically loaded semantic matters, and allows us to see that the phenomenon of and involving rigidity - especially the necessary a posteriori - are of no metaphysical significance on their own.

The Aristotelian doctrine of hylomorphism has seen a recent resurgence of popularity, due to the work of a number of well-known and impressive philosophers. One of the recently motivating virtues claimed for the doctrine is its ability to solve the grounding problem for philosophers who believe in coinciding entities. In this brief article, I will argue that when fully spelled out, hylomorphism does not, in fact, contribute a distinctive solution to this problem. It is not that it offers no solution at all, but that it is not really a different solution from other familiar, seemingly non-hylomorphic, solutions on offer

Most contemporary internalists are fallibilists, denying that there need be anything about which we are infallible for us to have knowledge or justified beliefs. At the same time, internalists standardly appeal to ‘internal twins’ in arguing against externalism and motivating internalism---a Cartesian demon can ruin the ‘external’ relations we have to the world, but one is equally well justified in one’s beliefs whether or not one is subject to such deception. Even if one doesn’t motivate one’s internalism by appeal to internal twins, any internalist must agree that internal twins are equally well justified in their beliefs. I argue that the internal twins argument for, or commitment of internalism, commits one to the claim that the conditions in virtue of which one is justified must be ones about which a believer is infallible. The basic argument is that for anything about which one can be mistaken, one has an internal twin who is mistaken, but is equally well justified---and so, not in virtue of that about which one can be mistaken. If the argument can be resisted, this should tell us something useful about how to properly understand both internalism in general, and the idea of internal twins in particular