Abstract

Moral conclusions cannot validly be inferred from nonmoral premises – this principle, commonly called “Hume’s law,” presents a conundrum. On one hand, it seems obviously true, and its truth is often simply taken for granted. On the other hand, an ingenious argument by A. N. Prior seems to refute it. My aim here is a resolution. I shall argue, first, that Hume’s law is ambiguous, admitting both a strong and a weak interpretation; second, that the strong interpretation is false, as shown by Prior’s argument; and, third, that the weak interpretation is true.