We have the power to make dramatic moral differences with words. In particular, certain speech acts - apologies, forgiveness, peace agreements - change the moral dynamics between people, thereby restoring relationships, relieving moral debts and grounding historic reconciliation. Few dispute this power, even as it continues to amaze us in practice. Yet, despite an illuminating burst of scholarly attention to many aspects of apology, forgiveness and moral repair in recent years, their power remains elusive. That is, we still have an incomplete grasp of what, exactly, about saying "I'm sorry," or "I forgive you" effects such significant moral change. The dissertation seeks to understand and account for that power. At the same time, it also seeks a new account of these speech acts and their sincerity conditions, not only for individual people but for corporate and institutional bodies, as well. These twin projects are joined by the same underlying conviction: to capture how these speech acts accomplish so much, we need a new understanding of what they are. Chapters I and II begin this explanatory project by focusing on the classic case of apologies, taking issue with traditional accounts of apologetic expression as representing or revealing something - such as how the speaker feels or what she believes. These views cannot make sense of the way an apology responds remedially to a past wrongdoing, as illustrated most dramatically by cases where the victim knows everything the apology could reveal. Instead, I argue that apologies, and similar speech acts, should be understood less as expressions than as ways of treating someone that counteract the mistreatment begun by the actions for which one apologizes. This model requires a new, relational understanding of both apologies and of the actions that give rise to them. Chapter III focuses on the formal speech act of forgiveness, by which a victim can alter the moral status of her offender - rendering apologies and other acts of moral repair unnecessary, and their absence no longer blameworthy. I argue that forgiveness has this impact because, and to the extent that, it takes place in contexts in which the moral power of other remedial steps like apology are already at work. As with apologies, then, forgiveness emerges as less a unilateral expression than an interactive approach to another person, which can help restore their relationship. Together the accounts present apologies, forgiveness and similar speech acts as active ways for people to relate to each other, whose sincerity depends more on commitments and dispositions to act than on emotions and psychological states. With this framework in place, it becomes clear why even institutions - countries, courts, companies - can sincerely apologize, forgive and engage each other in similar speech acts, as I argue in Chapter IV. The resulting picture of utterances like apology and forgiveness departs from the speech-action dichotomy that Austin and Searle began challenging half a century ago. On the account developed here, certain speech can function as action over and above what it communicates, while some actions have meaning beyond their material impact on the world. The area of moral repair, then, sheds new light on what action can mean and speech can do.