Alan Sidelle

The phenomenon of rigid designation - in particular, de jure rigidity - is typically treated metaphysically. The picture is: reference is gained in a way that puts no constraints on what an object in other worlds, or counterfactual situations must be like, in order to be the referent of that term, other than 'being this thing'. This allows 'pure metaphysical' investigation into, and discovery of 'the nature' of the referent. It is argued that this presupposes a 'privileged' ontology, of a sort that is far from obvious. An alternative picture of rigidity is sketched, terms have associated criteria of identity and criteria of application for counterfactual situations. A term is rigid when these coincide. Aside from being a better account of rigidity, it also undermines the picture of rigid terms allowing us to 'metaphysically' investigate the nature of the referent: matters of identity and essence for the referent are settled by these semantic constraints (though it can be done in a way that allows are a posteriori necessities).

One common objection to Conventionalism about modality is that since it is contingent what our conventions are, the modal facts themselves will thereby be contingent. A standard reply is that Conventionalists can accept this, if they reject the S4 axiom, that what is possibly possible is possible. I first argue that this reply is inadequate, but then continue to argue that it is not needed, because the Conventionalist need not concede that the contingency of our conventions has any bearing on the modal status of necessary truths. It is explained why this does not compromise the Conventionalist claim that necessity – and particularly, essence – is due to conventions

Philosophy and science employ abstract hypothetical scenarios- thought experiments - to illustrate, defend, and dispute theoretical claims. Since thought experiments furnish no new empirical observations, the method prompts two epistemological questions: whether anything may be learnt from the merely hypothetical, and, if so, how. Various sceptical arguments against the use of thought experiments in philosophy are discussed and criticized. The thesis that thought experiments in science provide a priori knowledge through non-sensory grasping of abstract entities is discussed and rejected. The thesis that thought experimentation consists in manipulations of mental models is examined and found to be of limited epistemological relevance. It is argued that thought experiments are associated with characteristic arguments in a manner similar to ordinary experiments. It is further argued that thought experiments function in the same way as experiments in general: by providing premises for their associated arguments. Like other experiments, a thought experiment is successful when the premises it provides are true. This holds both for philosophical and scientific thought experiments. An argument schema is proposed and shown to be a formal analogue to that associated with ordinary experiments; similar in being subject to epistemological holism; but differing in being modal: in employing statements about possibility and necessity. The evaluation of thought experiments thus depends on how modal statements may be justified. Intuition and conceivability are discussed as sources of modal justification and found problematic. Instead it is suggested that evaluation proceed by accommodation of the statements describing the experiment's hypothetical scenario. The method of accommodation is developed and applied to five influential thought experiments in philosophy: the brain in a vat; Putnam's Twin Earth; Burge's arthritis example; Searle's Chinese Room; and Newcomb's problem. Its application shows some of these to be failed, others to be successful only relative to controversial philosophical doctrines

ABSTRACT: Rudolf Carnap’s “Empiricism, Semantics and Ontology” (ESO) has received a good deal of sympathetic interest over the years from philosophers who are not particularly sympathetic to verificationism, or suspicious of metaphysics in general. Recent work has favorably cited ESO in connection with doubts about the genuine content of debates in the metaphysics of material objects. But, when we look at how Carnap introduces his central notion of a ‘framework’, and the questions he wants to use it to deflate, there seem to be significant differences in his approach and aim from that of contemporary deflationists about the metaphysics of material objects. This paper first looks at some of these differences, and suggests a way of seeing them as arising more from differences in focus and interest than fundamental approach. However, a further question is whether philosophers who may entirely disagree with Carnap about abstract entities, or the substantiveness of the debate between Realists and Idealists – possibly all of his negative conclusions in ESO - can really be seen as heirs to his approach and argument therein. We look first at his discussion of the Realism/Idealism debate, to sort out different aspects of his analysis, and determine to what extent one can disagree with it while not thinking this undermines other analyses using the same general strategy. In the course of this, we are able to distinguish the basic Carnapian analysis of metaphysical disputes, from the question of whether, if the analysis is correct, this actually subverts the disputes. I suggest that, if we put verificationism aside, ESO really provides us with an approach and a type of skeptical challenge more than an argument, and it is open to contemporary philosophers to think that this skeptical challenge can (or can’t) be met, or can be supplemented by further argument, on a case by case basis.

A not-unpopular position in the metaphysics of material objects (Ted Sider's, for instance) combines realism about what objects there are and the conditions of objecthood with conventionalism about de re modality. I argue that this is not a coherent combination of views: one must go fully conventionalist, or fully realist. The central argument displays the difficulty for the modal conventionalist/object realist in specifying the object that satisfies de re modal predicates. I argue that if this is a mind-independent object, contradictions arise when we consider the possibility or actuality of non-equivalent conventions both applying to 'the same object'.

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 intrinsicness via duplication cases.