ABSTRACT
There is a celebrated discussion of the distinction between the natural and the conventional in Aristotle's Nichomachean Ethics: There are two forms of justice, the natural and the conventional. Many philosophers in the time would dispute the last statement of Aristotle's, being of the opinion that justice is conventional in all its branches. Like the Sophistic thinkers to whom Aristotle was referring, Karl Popper lays great stress on the alleged fact that whereas norms of behaviour are variable and alterable, laws of nature are not. This chapter shows that Popper fails to establish his desired dualism; and argues that there are certain aspects of morality which make it necessary to say that it is not entirely based on convention but that, on the contrary, it is presupposed by any possible conventions. Such a view need not imply, as Popper thinks it must, the nonsensical idea that norms can be laid down ‘in accordance with natural laws’ in the scientific sense.
