The paper sketches an epistemology of de re possibility centred on the notion of similarity. The proposal is, roughly, that we know about some entities’ unrealized possibilities by extrapolation from knowledge about some other, similar entities’ realized possibilities. The account is limited, among other things, in that it does not cover knowledge of de re necessities or essentialist knowledge, if we have it. But even if alternative epistemologies could explain that type of knowledge too, the current account is found to (...) best explain the de re possibility knowledge, thereby resisting a potential charge of redundancy. (shrink)