Brian Weatherson

Sameness and Substance Renewed (hereafter, 2001) is, in effect, a second edition of Wiggins’s 1980 book Sameness and Substance (hereafter, 1980), which in turn expanded and corrected some ideas in his 1967 Identity and Spatio-Temporal Continuity (hereafter, 1967). All three books have similar aims. The first is to argue, primarily against Geach, that identity is absolute not relative. The second is to argue that, despite this, whenever an identity claim a = b is true, there is a sortal f such that a is the same f as b. The biggest difference between 1967 and the two later books is that the later books contain much more detail on what a sortal must be if this claim, called D, is to be both correct and philosophically interesting. The third aim is to apply the first two conclusions to the topic of personal identity.

Ernest Adams has claimed that a probabilistic account of validity gives the best account of our intuitive judgements about the validity of arguments. In particular, he claims, it has the best hope of accounting for our judgements about many arguments involving conditionals. Most of the examples in the literature on this topic have been arguments framed in the language of propositional logic. I show that once we consider arguments involving predicates and involving identity, Adams’s strategy is less successful

Barrett and Artzenius posed a problem concerning infinite sequences of decisions. It appeared that the strategy of making the rational choice at each stage of the game was, in some circumstances, guaranteed to lead to lower returns than the strategy of making the irrational choice at each stage. This paper shows that there is only the appearance of paradox. The choices that Barrett and Artzenius were calling ‘rational’ cannot be economically justified, and so it is not surprising that someone who makes them ends up with sub-optimal returns. A solution to the more general problem they pose is also advanced.

Over the last two decades, William Lycan’s work on the semantics of conditionals has been distinguished by his careful attention to the connection between syntax and semantics, and more generally by his impeccable methodology. Lycan takes compositionality seriously, so he requires that the meaning of compound expressions like ‘even if’ be a combination of the constituent expressions, here ‘even’ and ‘if’. After reading his work, it’s hard to take seriously work that does not share this methodology.

Humean supervenience is the conjunction of three theses: Truth supervenes on being, Anti‐haecceitism, and Spatiotemporalism. The first clause is a core part of Lewis's metaphysics. The second clause is related to Lewis's counterpart theory. The third clause says there are no fundamental relations beyond the spatiotemporal, or fundamental properties of extended objects. Supervenience is classified into strong modal Humean supervenience, local modal Humean supervenience and familiar modal Humean supervenience which states that: for any two "worlds like ours", if the spatiotemporal distribution of fundamental qualities is the same at each world, the contingent facts are also the same. The fact that quantum mechanics raises problems for Humean supervenience does not undercut the philosophical significance of Lewis's defense of Humean supervenience. Humean supervenience says that in a world like ours, the fundamental properties are local qualities: perfectly natural intrinsic properties of points, or of point‐sized occupants of points.

Relativism is the view that the truth of a sentence is relative both to a context of utterance and to a context of assessment. That the truth of a sentence is relative to a context of utterance is uncontroversial in contemporary semantics. This chapter focuses on three points: whether the version of contextualism is vulnerable to the disagreement and retraction arguments, and if so, whether these problems can be avoided by a more sophisticated contextualist theory. The points include: whether relativism really does avoid the four problems posed for the other theories; and whether there are other theories that also avoid the problems, without running into the problems facing relativism or problems of their own. The chapter concentrates on two families of views that have been called relativist: Relativism about propositional truth; and Relativism about utterance truth.