At the start of Plato’s Minos an anonymous comrade argues that the variability of law according to time and place undermines the claim that it conveys moral truth. But by the end he has accepted Minos as the greatest of lawgivers because of his education by Zeus. How does he manage to slide so quickly from the moral laxity of conventionalism to the moral absolutism of divine revelation? Guided by this question, the author considers how the two divergent parts of the Minos form one whole, and so what Plato suggests is the common basis to conventionalism and piety. Plato’s Minos thus ends up having an unexpectedly close relationship to his Euthyphro.