This entry provides a brief overview of the history of the term “moral certainty,” presents contemporary accounts of moral certainty, and addresses objections to these accounts. The term “moral certainty” has negative connotations. Dogmatism comes to mind, and claims to moral infallibility. The Oxford English Dictionary defines moral certainty as “a degree of probability so great as to admit of no reasonable doubt.” In the seventeenth century, the term became prominent in the legal context. More recently, some moral philosophers interested in Wittgenstein's relevance for ethics have given the term a new meaning. They use it to refer to the moral analogue of the phenomenon Wittgenstein is concerned with in his On Certainty. Wittgenstein considers cases in which something – for instance, the existence of his hands in ordinary circumstances or the existence of the earth long before he was born – seems to be both beyond reasonable doubt and beyond justification. He argues that what can be neither doubted nor justified is not an item of knowledge, but of certainty. Arguably, something analogous exists in the moral realm. For morally competent agents, it is, for instance, certain that it is morally required to rescue the child in Peter Singer's pond example. Morally competent agents have no reasons to doubt this, and at the same time are not able to provide reasons that are more certain than what they are supposed to support. Moral certainty is not propositional, but “enacted” – i.e., manifested in how morally competent agents speak and act.