In The World Without, the Mind Within, André Gallois points out that the inference from ‘p’ to ‘I believe that p’ is neither deductively valid nor inductively strong. This is (a version of) the puzzle of transparency—how can such an inference yield knowledge? This chapter examines the puzzle in depth, as it arises for belief, perception, and sensation. Gallois’s own solution to the puzzle is criticized, as are those offered by Richard Moran and Fred Dretske. The puzzle of transparency in the special case of sensations is also discussed, as is the puzzle’s connection with the problem of other minds as discussed by Kripke in Wittgenstein on Rules and Private Language, and with Hume’s remarks on the self in the Treatise.