I introduce and defend the semantic notion of counterfactual identity, distinguishing it from the metaphysical notion of transworld identity. After showing that Lewis's counterpart theory misconstrues counterfactual identity facts, I outline and motivate a ‘Leibnizian counterpart theory’ where the notion of counterfactual identity is adequately modelled. Finally, I show that counterfactual identity can be characterized without relying on some implausible features of Lewis's theory of conditionals.

Moore's Open Question Arguments are among the most influential arguments in 20th Century metaethical thought. But, surprisingly, there is a fair amount of confusion concerning what the Open Question Arguments actually are, how the Moorean passages should be interpreted, and what they are intended to show. Thus, the early chapters are devoted to clarificatory matters, including the exposing of a variety of contemporary attacks upon Moore's arguments as misguided by indicating where they rest upon faulty interpretations of Moorean passages. Providing (...) what I take to be accurate formulations of Moore's famous arguments, responding to historically important preliminary objections, and, finally, presenting various shortcomings of these arguments constitute the remaining themes of the early chapters. ;Next, I pursue an explanation of what I call the 'Open Question phenomenon': the inclination that many have to endorse Moore's "open question" premises. I survey a variety of popular noncognitivist explanations, arguing that each of them is unsatisfactory. I then present a novel semantic explanation of the phenomenon and use it to construct an augmented Moorean Open Question Argument, one capable of overcoming the shortcomings of Moore's originals. ;The latter chapters are dedicated to an investigation of Moore's preferred normative theory---a version of objective consequentialism. I argue that the standard semantic account of subjunctive conditionals fails to capture the nature of certain subjunctive conditionals relevant to the normative evaluation of alternatives from an objective consequentialist perspective. I then present a modified version of the standard account in an effort to remedy the problem. ;Next, I present a novel objection against all extant versions of objective consequentialism. I then introduce and utilize the concept of an "objective" subjunctive probability in the transformation of a subjective version of consequentialism into an objective version, one capable of dealing with the difficulties posed by the objection. ;I conclude the dissertation with a final chapter in which I defend possibilist versions of consequentialism from a contemporary objection. In doing so, I elucidate a theoretical advantage that possibilist theories have over their subjunctive counterparts. (shrink)