The claim of this paper is that the everyday functions of knowledge make most sense if we see knowledge as contrastive. That is, we can best understand how the concept does what it does by thinking in terms of a relation “a knows that p rather than q.” There is always a contrast with an alternative. Contrastive interpretations of knowledge, and objections to them, have become fairly common in recent philosophy. The version defended here is fairly mild in that there (...) is no suggestion that we cannot think in terms of a simpler not explicitly contrastive relation “a knows that p.” Some, for instance Schaffer (2005) and Karjalainen and Morton (2003), have hinted that this stronger possibility may be right. But all that I am arguing now is that facts that are easily expressed in contrastive terms are vital to understanding why we need the concept of knowledge. In a piece that is in some ways a companion to this one ("Contrastivism" in Duncan Pritchard and Sven Bernecker, eds. The Routledge Companion to Epistemology. Routledge 2010, 513-522), I give a general survey of theories of contrastive knowledge and the differences between them. (shrink)