The idea for the present work came to me, perhaps appropriately, on April Fools’ Day, 2017, at the conclusion of a meeting in Cologne of the International Sociological Association Research Committee 28 on Social Stratification and Mobility.

Some months previously, I had published a book, Sociology as a Population Science, in which my main concern was, as I put it (2016: 2), ‘not to propose to sociologists how they should conceive of and practise their subject’ but rather ‘to suggest a way in which a fuller and more explicit rationale than has hitherto been available might be provided for what a large and steadily growing number of sociologists already do – although, perhaps, without a great deal of reflection on the matter’.