Here’s the riff (developed from the paper I delivered at the recent AAP conference): because the success* of behavioural strategies – including moral strategies – depends on the environmental conditions in which the agent is situated, and because that environment includes the strategies employed by other agents, it pays to Mix It Up A Bit in terms of the strategies employed by the population.
As a result, you’d expect to see a diversity – or a ‘pluralism’ or ‘polymorphism’ – of strategies employed in a population. Some will be ‘nice’, some will be ‘suspicious’. That’s what I call Lesser Moral Diversity. Some will be ‘nice’, some ‘suspicious’, some ‘nasty’. That’s what I call Greater Moral Diversity. Details below: