According to hedonistic act utilitarianism, an act is morally right if and only if, and because, it produces at least as much pleasure minus pain as any alternative act available to the agent. This dissertation gives a partial defense of utilitarianism against two types of objections: action guidance objections and intuitive objections. In Chapter 1, the main themes of the dissertation are introduced. The chapter also examines questions of how to understand utilitarianism, including (a) how to best formulate the moral (...) explanatory claim of the theory, (b) how to best interpret the phrase "pleasure minus pain," and (c) how the theory is related to act consequentialism. The first part (Chapters 2 and 3) deals with action guidance objections to utilitarianism. Chapter 2 defines two kinds of action guidance: doxastic and evidential guidance. It is argued that utilitarianism is evidentially but not doxastically guiding for us. Chapter 3 evaluates various action guidance objections to utilitarianism. These are the objections that utilitarianism, because it is not doxastically guiding, is a bad moral theory, fails to be a moral theory, is an uninteresting and unimportant moral theory, and is a false moral theory. The second part (Chapters 4, 5 and 6) deals with intuitive objections to utilitarianism. Chapter 4 presents three intuitive objections: Experience Machine, Transplant, and Utility Monster. Three defenses of utilitarianism are subsequently evaluated. Chapter 5 and 6 introduces two alternative defenses of utilitarianism against intuitive objections, both of which concern the role that imagination plays in thought experimentation. In Chapter 5, it is argued that we sometimes unknowingly carry out the wrong thought experiment when we direct intuitive objections against utilitarianism. In many such cases, we elicit moral intuitions that we believe give us reason to reject utilitarianism, but that in fact do not. In Chapter 6, it is argued that using the right kind of sensory imagination when we perform thought experiments will positively affect the epistemic trustworthiness of our moral intuitions. Moreover, it is suggested that doing so renders utilitarianism more plausible. In Chapter 7, the contents of the dissertation are summarized. (shrink)