 How does reason enter the matter? In the famous “Refutation of Idealism,” Kant says the following: “Whether this or that putative experience is not mere imagination [or dream or delusion, etc.] must be ascertained according to its particular determinations and through its coherence with the criteria of all actual experience” (B279). To see what Kant means, consider a simple example. Suppose that our dreamer believes she has won a lottery, but then starts to examine this belief. To decide its truth, she must ask how far it connects up with her other judgments, and those of other  people.[4]  If it fails to connect up (she checks the winning numbers, say, and sees no match with her actual ticket), she must conclude that the belief was false. Otherwise, she would contradict a fundamental law of possible experience, that it be capable of being unified. As Kant summarizes his position: “ the law of reason to seek unity is necessary, since without it we would have no reason, and without that, no coherent use of the understanding, and, lacking that, no sufficient mark of empirical truth…”  (A651/B679).[5] 