This dissertation explores ontological and ethical issues related to speech acts. The primary focus is on promises. I begin by asking the question, What is a promise? In response to this question, I develop and defend an account of promises according to which promises do not necessarily generate promissory obligations. With this understanding of promises in mind, I move on to the question, Which promises generate promissory obligations? Two kinds of promises are investigated in depth: sexual promises and political campaign promises. I identify two novel problems with sexual promises and argue that these promises do not generate promissory obligations. In contrast, I argue that while campaign promises are distinct from ordinary promises in a number of important ways, they are best explained as instances of morally obligating promises. Finally, I examine the relationship between conditional promises and conditional threats, and draw on resources from the promissory literature to sketch the foundations for an account of conditional threats.