John Dupre explores the ways in which we categorize animals, including humans, and comes to surprisingly radical conclusions. He opposes the idea that there is only one legitimate way of classifying things in the natural world, the 'scientific' way. The lesson we should learn from Darwin is to reject the idea that each organism has an essence that determines its necessary place in the unique hierarchy of things. Nature is not like that: it is not organized in a single system. There is no universal principle by which organisms can be sorted into species; still less is there any unique way of classifying kinds of humans. We are obliged to accept that different classificatory schemes are valid for different purposes, and therefore to take a pluralistic view of biology and the human sciences. These provocative and readable essays move on to discuss a set of contentious topics relating to human nature. To start with, Dupre argues that the concept of a universal human nature should be rejected. He questions the relevance of evolution to explanation of human behaviour, and casts doubt on the concept of normality in human behaviour.
He shows that misunderstanding of biology and evolution has led to widespread misconceptions about human sex and gender - in particular, about sexual behaviour and gender roles. The book concludes with a pair of essays about the differences between humans and animals - which may not be quite so clear-cut as we think.