Every philosopher knows of the “freshman relativist”, quick to assert, dogmatically even, that it all depends how you look at it; if they think that then it must be true for them; when in Rome…; and at the end of the line, just “wha’ever”. You do not have to own a signed photograph of Michael Gove to loathe and fear this cynical or sceptical character.

Yet for a long time the “postmodernist” climate nurtured the relativist frame of mind. Hidden dark forces mould and skew our beliefs and even our perceptions, let alone our values and tastes. We are each the creation of a particular history and culture, class and gender. There is no reason to expect uniformity, or convergence towards it. Multiplicity and diversity rule, and a good thing too. We should no longer entertain imperial ambitions, blithely supposing that just one ethic, or ideology, or way of life is the right one for everybody, and still less that we have the right to impose it on everybody.

The relativist frame of mind was not new in the late twentieth century. It was the target of some of Plato’s most impressive writings. Indeed Socrates’s celebrated rebuttal, the so-called “peritrope” has been a standard weapon in any anti-relativist armoury. The idea is to get the relativist to assert his position, claiming, for instance, that what seems true (or false) to anyone therefore is true (or false) for them. We then reply that this claim seems false to us, hence by its own lights it is false for us, and thus we refute it. Although Plato shows Socrates’s opponents being dumbfounded by this turning of the tables, it is hard to believe that such a quick victory ever won many converts.