A familiar feature of our moral responsibility practices are pleas: considerations, such as “That was an accident”, or “I didn’t know what else to do”, that attempt to get agents accused of wrongdoing off the hook. But why do these pleas have the normative force they do in fact have? Why does physical constraint excuse one from responsibility, while forgetfulness or laziness does not? I begin by laying out R. Jay Wallace’s (Responsibility and the moral sentiments, 1994 ) theory of (...) the normative force of excuses and exemptions. For each category of plea, Wallace offers a single governing moral principle that explains their normative force. The principle he identifies as governing excuses is the Principle of No Blameworthiness without Fault: an agent is blameworthy only if he has done something wrong. The principle he identifies as governing exemptions is the Principle of Reasonableness: an agent is morally accountable only if he is normatively competent. I argue that Wallace’s theory of exemptions is sound, but that his account of the normative force of excuses is problematic, in that it fails to explain the full range of excuses we offer in our practices, especially the excuses of addiction and extreme stress. I then develop a novel account of the normative force of excuses, which employs what I call the “Principle of Reasonable Opportunity,” that can explain the full range of excuses we offer and that is deeply unified with Wallace’s theory of the normative force of exemptions. An important implication of the theory I develop is that moral responsibility requires free will. (shrink)