For what it is worth, when I was being introduced by Jonathan Miller of the B.B.C. program last month, he said: "McLuhan is doing for visual space what Freud did for sex". Flattery apart, that does make sense to me. Freud revealed the pervasiveness of sex as structure in experience and environment and in situations that seem to have just nothing at all to do with sex. As soon as you begin to deal with the sensory modalities, you quickly discover that the visual mode may occur in situations that are quite unvisualizable. For example, central heating structures the thermal space of a room visually. That is, a centrally heated room has a thermal space that is uniform, and continuous, and connected. That is visuality as such.