“Ought” and “Is”

Abstract

There is probably no student of modern philosophy, and certainly no listener to the Third Programme, who has never received the warning that he must on no account deduce an “ought” from an “is.” This prohibition, it is claimed, is securely based in established and unchallengeable principles of logic. Professor Flew was speaking for many others when he said, in the course of a broadcast entitled “Problems of Perspectives”, “I think it is very important indeed to make as clear as we can and to underline with all possible emphasis that this is a point of inexorable logic”. And Professor Popper, to take but one other example, has expressed himself no less trenchantly: “Perhaps the simplest and most important point about ethics is purely logical, I mean the impossibility to derive nontautological ethical rules—imperatives, principles of policy, aims or however we may describe them—from statements of fact”—a view that is fully endorsed by Mr. Hare in his Language of Morals.