While Hebb was working out his ideas in Canada, Hayek was theorizing towards similar ends in Britain, from very different psychological and philosophical traditions. The Sensory Order (1952), the book we draw on in this chapter, is subtitled An Enquiry into the Foundation of Theoretical Psychology. It was an interesting excursus for the author – his world-wide reputation was built on such works as Monetary Theory and the Trade Cycle, Profits, Interests and Investments, and The Pure Theory of Capital. Hayek used his economist’s interest in building theories on the basis of relatively few data to construct a set of hypotheses about the kind of activities and relationships we must imagine among the nerve-cells, if these are to fulfil their function of enabling us to lead our lives in an organized way. This set of hypotheses forms his theory. In the logicomathematical tradition, he numbers each of his paragraphs, first by chapter and then by its order within the chapter. I have retained this usage for easy reference, and I have sometimes taken the liberty of simplifying or abbreviating an excerpt.