Alan Sidelle

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

Some relations - like supervenience and composition - can appear very much like identity. Sometimes, the relata differ only in modal, or modally-involved features. Yet, in some cases, we judge the pairs to be identical (water/H2O; Hesperus/Phosphorus), while in others, many judge one of the weaker relations to hold (c-fiber firing/pain; statues/lumps). Given the seemingly same actual properties these pairs have, what can justify us in sometimes believing identity is the relation, and sometimes something weaker? I argue that it can only be knowledge of differences of individuative criteria that we know a priori because they are built into the meanings of the words/concepts involved. Possible metaphysical conclusions are considered.

One obvious solution to the puzzles of apparently coincident objects is a sort of reductionism - the tree really just is the wood, the statue is just the clay, and nothing really ceases to exist in the purported non-identity showing cases. This paper starts with that approach and its underlying motivation, and argues that if one follows those motivations - specifically, the rejection of coincidence, and the belief that 'genuine' object-destroying changes must differ non-arbitrarily from accidental changes, that one can plausibly be pushed to an extreme nihilism, that denies the existence of any objects at all.

This paper defends the traditional view that the laws of nature are contingent, or, if some of them are necessary, this is due to analytic principles for the individuation of the law-governed properties. Fundamentally, I argue that the supposed explanatory purposes served by taking the laws to be necessary --showing how laws support counterfactuals, how properties are individuated, or how we have knowledge of properties--are in fact undermined by the continued possibility of the imagined scenarios--this time, described neutrally--which seemed to disprove the claim to necessity in the first place. I speculate that this will be true for any proposed necessary a posteriori truths, and is a basis for rejecting their supposed metaphysical significance.

Many philosophers believe that identity through time cannot depend on features extrinsic to the relata and relations between them. This goes with the view that one must deny identity in cases for which there is a ‘duplication case’-a case just like the first, but for an additional, ‘external’ element which provides an equal or better ‘candidate’ for identity with one of the relata. Such friends of intrinsicness cannot remedy the failure of continuity of function/form to be one-one by non-branching or closest competitor clauses. The obvious intrinsic approach-perhaps taken for granted-appeals to considerations of quantity of matter, requiring over 50% shared matter between identicals . But this rules out plausible cases of halving and doubling for which there are not duplication cases. After bringing out this problem, I ask what makes duplication cases possible, and use this to formulate an intrinsic condition which allows identity whenever there is continuity of function, but no threat to intrinsic ness via duplication cases