What in the world is weakness of will?

At least since the middle of the twentieth century, philosophers have tended to identify weakness of will with akrasia—i.e. acting, or having a disposition to act, contrary to one’s judgments about what is best for one to do. However, there has been some recent debate about whether this captures the ordinary notion of weakness of will. Richard Holton claims that it doesn’t, while Alfred Mele argues that, to a certain extent, it does. As Mele recognizes, the question about an ordinary concept here is one apt for empirical investigation. We evaluate Mele’s studies and report some experiments of our own in order to investigate what in the world the ordinary concept of weakness of will is. We conclude that neither Mele nor Holton (previously) was quite right and offer a tentative proposal of our own: the ordinary notion is more like a prototype or cluster concept whose application is affected by a variety of factors.