Pursuing last week’s theme, this week’s column raises the question: if there is no such thing as ‘race’ — since all humans belong to the same subspecies — why is there such a thing as racism? The modern answer is that race is (yawn) a ‘social construct’. But in the light of a famous passage in the 5th century BC by Thucydides, there is a case for saying that racism is the antisocial construct.