Imagine a conference held on 'The idea of race' around 1930 and a discussion between a race theorist and a sceptical opponent of race theory. In order to bolster the claims of race theory to be a science, the race theorist points to a massive body of work produced by European scholars, studies that use systematic observation, precise measurement and statistical methods involving hundreds of subjects. To this the sceptic replies that there is no need to postulate essences called 'races' in order to explain - if explanation is needed - the physical differences between groups of humans found in different parts of the world. No doubt the retort to this from the race theorist would be: what do you propose to put in the place of the concept of race?