 Diderot is heavily influenced by Locke and in general by a kind of empiricism that was “in the air”: our knowledge about the world is derived, either fully or at least in large part, from our senses. In the Lettre sur les aveugles and its companion piece, the Lettre sur les sourds et muets, as well as later pieces such as the Rêve, Diderot turns the question of the senses and how we know the external world on its head: the senses possess or carry with them their own respective metaphysics. It is a powerful kind of relativism. And there is a new hierarchy in which touch is fundamental, in direct opposition to classical philosophical doctrines in which sight received that honour: throughout his work, but especially in these two essays devoted to the metaphysics of the senses and his various aesthetic writings, Diderot insists on the primacy of touch, which he also describes as “the most philosophical of senses”; he deplores the fact that “the hands are despised for their materialism” (LSM; DPV IV: 15, 54). This is even given atheist overtones in the Lettre sur les aveugles when the blind mathematician Saunderson on his deathbed declares that “if you wish me to believe in God, you will have to make me touch him” (DPV IV: 48).