[zerospinboson]

Originally Posted by Patricia

Actually, G E Moore's Principia Ethica agrees that you cannot move from is to ought, but holds that 'Good' is indefinable, but recognised via intuition.

That way neatly making it impossible to say anything at all about the subject, as the only requirement is that something is "intuited" by some "moral sense".
Philippa Foot, in Natural Goodness, says this on the argument:

One finds its deepest roots in David Hume. But more immediately, Ayer and Stevenson's emotivism, like Hare's prescriptivism, came into being as a result of the 'linguistic turn', popularized by logical positivism but developing far beyond it. For with 'linguistic philosophy' came the idea of explaining the singularity of moral judgement in terms of a special use of language, called 'evaluation' but more akin to exclamation and command than to anything one would normally mean by that term. With this idea it seemed possible, at last, to say clearly what G. E. Moore had meant, or should have meant, when he insisted that goodness was a special kind of 'non-natural' property. In the development of emotivism and prescriptivism the idea of a special ('non-natural') property was replaced by that of a special and essentially practical use of language. And this, it seemed, was a great discovery. The language of evaluation was 'emotive'. It expressed a speaker's feelings and attitudes, as well as inducing similar feelings and attitudes in others. Those who had these 'attitudes' 'favoured' the things they called 'good': the idea of an attitude being linked to a tendency to act. Such also was Ayer's doctrine; and a little later Hare tied 'evaluation' even more closely to individual action, in his theory of universalized imperatives by which a speaker exhorted others and, in the acceptance of a first-person imperative, committed himself to choose what he called 'good'. So 'prescriptivism'—a distinctive version of the doctrine that I have in my sights—was added to the emotivism with which it had started out.
[...]
In early versions of these theories it was suggested that only a demand for consistency set any limits on the classes of actions to which words such as 'morally good' or 'morally bad' could be applied. So the extra feature supposedly involved in moral judgement could stand on its own, ready to form the core of alien moral systems confronting, or even directly contradicting, our own; if no linguistic device existed for expressing 'moral approval' or 'moral disapproval' in their purity, this was held to be merely an accident of language. Thus these early theories were radically subjectivist, allowing the possibility even of bizarre so-called 'moral judgements' about the wrongness of running around trees right-handed or looking at hedgehogs in the light of the moon, and so opening up limitless possibilities of irresolvable moral conflict. Nowadays it is commonly admitted, I believe, that there is some content restriction on what can intelligibly be said to be a system of morality.

The whole problem with this being that it entirely ignored where these 'evaluations' came from, or what made them reasonable.
Luckily, we've moved beyond that ;-)

Originally Posted by Sparrow

How about the Bible story where Abraham is prepared to kill his son because his God tells him to? (That's always struck me as weird. )

Or worse, those stories where he commands the israelites to go out and subdue your neighbors by any means necessary (of Walls of Jericho fame).
Anyway, finding murder-happy stories in the OT is too easy.