A standard principle in ethics is that moral obligation entails ability, or that “ought implies can”. A strong case has been made that this principle is not well motivated in moral psychology. This paper presents an analogous case against the theoretical motivation for the principle. The principle is in tension with several foundational areas of ethical theorizing, including research on apologies, excuses, promises, moral dilemmas, moral language, disability, and moral agency. Across each of these areas, accepting the principle that obligation entails ability creates a theoretical problem that is more easily solved by rejecting it rather than accepting it. I conclude that the motivation for the principle is weak and that “ought implies can” should be rejected in ethics on theoretical grounds.