Universal Prescriptivism True
The nature of morality demands that it prescribe action.
R.M. Hare. “Objective Prescriptions.” Philosophical Issues, Vol. 4, Naturalism and Normativity, pg. 15-32. 1993.
The most common mistake of would-be objectivists is to treat the word 'objective' as if it meant the same as 'factual'. This mistake I have mentioned already. It is tempting to make it, because it looks as if the problem would be solved if we could show that moral statements state something objective in the sense in which ordinary matters of fact are objective.This amounts to the claim that moral statements are like many other kinds of statements (statements about the colour or shape of objects for example) in being purely descriptive of the world. Establish the moral facts, the idea is, and then all moral doubts will be at an end. But since that kind of purely factual objectivity or pure descriptivity is incompatible with prescriptivity, as we have seen, this claim amounts to the abandonment of the idea that moral statements are prescriptive. That is, they stop being guides to our actions. One can think that something is wrong, but then go on to say 'Yes, it is wrong; so what?'. This is one reason why this way of solving the problem will not do. Since the whole point of calling actions right or wrong is to provide a way of deciding whether to do them or not, if you abandon the prescriptivity of these moral statements you might as well stop making the statements. A non-prescriptive moral language has lost its function, except in so far as non-prescriptive uses are parasitical upon the prescriptive uses of other people, as where we call an act wrong, meaning no more than it is the sort of act that people call wrong.
As a prescriptive guide for action, morality must be universalizable.
R.M. Hare. “Universal Prescriptivism.” A Companion to Ethics, Blackwell Publishing, pg. 456. 1991.
The most-discussed kind of prescriptivism, known as universal prescriptivism, finds this differentia in what has been called the universalizability of 'ought'- sentences and other normative or evaluative sentences. Most descriptivists too acknowledge this feature of moral judgements. One cannot with logical consistency, where a and b are two individuals, say that a ought, in a certain situation specified in universal terms without reference to individuals, to act in a certain way, also specified in universal terms, but that b ought not to act in a similarly specified way in a similarly specified [similar in a similar] situation. This is because in any 'ought'- statement there is implicit a principle which says that the statement applies to all precisely similar situations. This means that if I say 'That is what ought to be done; but there could be a situation exactly like this one in its non-moral properties, but in which the corresponding person, who was exactly like the person who ought to do it in this situation, ought not to do it', I contradict myself (Hare, 1963, p. roff.). This would become even clearer if I specified my reasons for saying why it ought to be done: 'It ought to be done because it was a promise, and there were no conflicting duties'.
Moral judgments are only legitimate if they apply universally, to all relevantly similar actors and situations.
Don Locke. “The Principle of Equal Interests.” The Philosophical Review, Vol. 90, No. 4 (Oct., 1981), pp. 531-559.
It is, Hare argues, a consequence of the very logic of moral language that you cannot sincerely and consistently make a moral judgment unless, first, you are prepared to accept the same moral judgment in any relevantly similar situation, including those which affect you personally differently (this is universalizability),and second, you are willing to act in accordance with that judgment yourself, should you ever be in some such relevantly similar situation (this is prescriptivity). Indeed this is, as it stands,a tautology, since as Hare understands these things, consistency consists in being prepared to universalize your judgments, and sincerity consists in acting on them where you can.” It follows, then, that I cannot consistently assert a moral judgment unless I am prepared to act on it or have it acted on, should I be in the position of those to whom I am applying it: in Hare's celebrated example, I cannot sincerely and consistently assert that debtors ought to be imprisoned unless I am willing to be imprisoned myself, should I be a debtor. And this provides us, he believes, with a powerful weapon in moral argument: we simply ask people to imagine themselves in the position of those to whom they are applying their moral judgments and ask whether, supposing they were in that situation, they are still prepared to make the same judgment.