In 'Le Normal et le pathologique', an influential history of French medical thinking during the nineteenth century, Georges Canguilhem distinguishes between qualitative and quantitative conceptions of the normal. He finds the former in the writings of Lamarck, where life itself is defined as the dynamic capacity of an organism, not just to adapt to an environment, but to reshape that environment according to its own requirements. Understood thus, life itself is normative, and normativity is vital. Canguilhem regrets that this kind of thinking about the normal was not regularly practised by medical thinkers of the period. Instead, he says, they tended to engage in quantitative thinking. They defined the normal frequentatively, as that which occurs most often, or distributively, as a quality shared by individuals clustered near the middle of the range. Canguilhem’s own history is itself thoroughly normative, marking a clear preference for the qualitative over the quantitative. Our history, which does not share his philosophical commitment, will draw attention to the fact that the two kinds of thinking of which he speaks persisted in quite unresolved ways, as a commodious and mutually sustaining set of contradictions. To exemplify that view, we will consider Alfred Kinsey’s studies of sexual behaviour, with particular attention to the complicated and contradictory ways in which they were received when first published.