One big debate in metaethics today is whether or not we can argue for the truth or falsity of value claims. Is it true that kicking babies is bad? Or eradicating ethnic groups (genocide)? Is it true that keeping promises is good? That being kind to animals is? That being one's brother's keeper is? That we should treat others as we would wish to be treated? So-called moral realists argue for the necessity of being able to claim that such statements, and a great many others, are either true or false for, if it turns out we can't, then it looks as if we have lost the possibility of believing in the rightness or wrongness of these and similar behaviors. And this seems to undermine the moral project (the possibility of selectively differentiating between a certain class of actions). Without the ability to grant validity to our moral claims, we seem to be at a loss to tell others to do or not do a whole class of actions which seem to demand just such differentiating capability from us if we are to get on, in a satisfying way, with our lives. Societies and communities stand on the capacity to make such differentiations and to defend them when we do so, i.e., to believe in the truth of our differentiations.

No one doubts that one can judge the prudential value or its lack in certain behaviors, of course. We can know if it's true that we should keep our promise to another if we come to believe that doing so will prompt some good result for ourselves, e.g., that they will keep promises in turn to us (something we wish or need them to do) or if keeping promises will yield other rewards for us. But if personal rewards are the name of the game, then it's not keeping promises that's good (the right thing to do) per se, but getting the reward. And doing something to get a reward for doing it seems to vitiate the claim of moral goodness because it allows us, when the desired reward may not be available, to disregard practices like promise keeping, indeed to pursue a policy of deliberately performing their opposites.

Moral realists want to say that moral value claims carry their own criteria for being true or false, criteria which are not the same as the benefits an agent may gain, or hope to gain, by acting in a prudentially good way. Prudential benefits are external to the presumed morally good trait or action while what makes them morally good (or not) must be intrinsic to them, part of their very nature. Making and acting on moral claims must be independent of personal benefit, the value-granting feature (the presumed property of moral goodness the action is thought to possess) existing somewhere and somehow within the act itself -- or in our description of it. It's the presence or absence of such an extra feature, a feature we discern by observation and inquiry and which we assert to be there in statements which are subject to true or false judgments, that makes any claim of moral goodness reliable (or not) and so fit to be acted on (or rejected).

Intuitionists suppose such extra features are recognized by us because we have a kind of sense of them when they are there, picking up whatever the goodness feature is in a fundamentally unanalyzable way. Just as we see colors and hear sounds and taste flavors, so, for intuitionists, we have a kind of parallel capacity to apprehend moral goodness. That was G. E. Moore's notion and the notion of others, like Henry Sidgwick, who followed him down the intuitionist path. But intuitionism lacks a certain respectability in the modern intellectual world. If we can't explain the intuitive mechanism, as we can explain how and why we see colors, etc., in some physically demonstrable way (as a function of our sensing faculties and as phenomena sensed and thus relayed to the brain), then the idea of intuitions of goodness just looks spurious . . .