It would be informative to discover how Damasio’s readers (and indeed mine too) have reacted to this invitation to reflection. If they are like the population sampled by sex researchers, some would find it hard to recall any such lust-filled moments, whereas others would be inundated with recent memories jockeying for occupation of the conscious mind. Some would doubtless find their desire triggered instantly by such parts of the whole as an ankle or leg, whereas a number might find it fuelled by the shoes worn. Others would only be excited slowly by a whole speaking and socially interacting personality.

The enormous variation in the reactivity of human sexual desire is why I use the term ‘enigma’ and is a feature that must be accommodated by any attempt to explain desire’s foundations. What are the implications of this wide spectrum of responses? Is there a healthy norm, while deviations to either side indicate that something is wrong? Accounts by individuals, both famous and not, on their experience of desire are invaluable in understanding how it works and they will be used widely throughout the following pages.