Section 1 articulates a genus-species claim: that knowledge is a kind of success from ability. Equivalently: In cases of knowledge, S’s success in believing the truth is attributable to S’s ability. That idea is then applied to questions about the nature and value of knowledge. Section 2 asks what it would take to turn the genus-species claim into a proper theory of knowledge; that is, into informative, necessary and sufficient conditions. That question is raised in the context of an important line of objection against even the genus-species claim; namely, that there is no way to understand the attribution relation so that it does all the work that it is supposed to do. Section 3 reviews several extant proposals for understanding the attribution relation, and argues that none of them are adequate for answering the objection. Section 4 proposes a different way of understanding the relation, and shows how the resulting view does resolve the objection. Section 5 completes the new account by proposing a way to understand intellectual abilities. Section 6 briefly addresses Barn Façade cases and lottery propositions. Section 7 briefly addresses a question about the scope of knowledge; in particular, it shows how the new view allows a neo-Moorean response to skepticism.