I recently completed an independent study with a student interested in Mackie’s error theory, and we spent a good deal of time discussing Mackie’s argument from relativity or disagreement. For those unaware, the late Australian philosopher John Mackie favored an error theory of morality, according to which, although our ordinary moral language presupposes that our moral beliefs can correspond to moral facts, there are not moral facts with which those beliefs correspond. So as Mackie understood it, if Matilda believes that capital punishment is wrong and Nancy believes capital punishment is not wrong, their disagreement is in reality only an apparent disagreement, since there is no fact about the wrongness of capital punishment that would render their disagreement intelligible. Mackie held that this error-theoretical account offers a better explanation of the apparent widespread intra- and intersocietal moral disagreement than the alternative, namely, that either Matilda or Nancy is guilty of irrationality, ignorance, misperception, etc., with respect to the alleged moral facts. Moral discourse is thus akin to fairy discourse: The parties to a moral disagreement are arguing, literally, about nothing, just as those who argue about whether fairies’ wings are translucent or opaque are arguing about nothing.
I’ve often felt that the disagreement argument is an important advance over the sophomoric and soft-headed “anthropological” argument that simply says (a) there’s lot of moral disagreement in the world, so (b) there are no objective moral facts or truths. Mackie’s point is that deep-seated disagreement is rationally intractable disagreement, resulting not from any failure of rationality by one of the parties but from the parties holding conflicting normative attitudes toward one and the same sort of act or policy. This is what distinguishes moral disagreement from factual or scientific disagreement: In a factual or scientific disagreement, we have a good idea about what sort of evidence would rationally settle the matter, but with fundamental moral disagreements, we not only can’t point to what sort of evidence would rationally settle the matter, there doesn’t seem to be *any* evidence that might settle it.
Now those in the moral realist camp have replies to Mackie. (Many of these can be found in David Brink’s “Moral Realism and the Foundation of Ethics.”) These include:
1. Anthropological evidence suggests a high degree of cross-societal moral agreement.
2. Many moral disagreements are really non-moral disagreements. (Matilda and Nancy in my example above may agree that capital punishment is wrong if it is often imposed on innocent people, but disagree about whether it is often imposed on innocent people.)
3. Apparent moral disagreements are often explicable by societies’ differing material circumstances. Society A and society B might agree that we should be generous to children, but what counts as adequate generosity in wealthy society A might differ greatly from what counts as adequate generosity in poorer society B.
4. The ‘in the same boat’ reply (as I call it): Because our factual or scientific beliefs are underdetermined by the evidence for them, factual or scientific disagreements are sometimes conflicts between opposing paradigms between which rational agreement should not be expected. (Notice this reply is less a vindication of moral facts than the claim that if there are facts at all, there might as well be moral facts.)
5. Individuals who agree at the level of general moral principle often fail to recognize, or having difficulty imagining, the implications of those principles.
I’d be curious to know if these replies to Mackie’s disagreement argument are convincing, but I’d also like to suggest another direction: The five replies above all try to give morality back its rational credentials by narrowing the scope of moral disagreement or by showing that such disagreement is not rationally intractable and can be explained in terms of the parties’ irrationality, ignorance, etc. But I worry that these kinds of replies are too ambitious. Why not acknowledge that some moral disagreement really is rationally intractable? Here’s what I have in mind: Suppose that there are disagreements like those Mackie envisions, disagreements traceable to conflicts between deeply held normative attitudes where neither party will be rationally moved an inch. Given the peculiar normative aspirations that moral beliefs have (their supposed universalizability, categoricity, etc.) and the fact that moral beliefs have implications about people’s behavior (that some may have to make sacrifices for the greater good, e.g.), might not there be deepseated psychological mechanisms that ‘protect’ individuals’ moral beliefs from rational dissuasion? In other words, can’t moral realists just say that some moral disagreement is rationally intractable and that such disagreement has a psychological explanation related to the close relationship between morality on the one hand and social order, identity, self-interest, etc., on the other? Obviously, such a position opens up a can of worms about how such disagreements would be rationally resolvable if they could be resolved (i.e., how one of the parties can be mistaken). But the usual realist replies seem utopian, suggesting that all moral disagreement turns out to be rational in the end. Perhaps I’m proposing a more realistic reply for realists!