Although the contemporary metaethics literature contains many references to (and discussions of) the late J.L. Mackie’s arguments against moral realism, I’ve never seen anyone formally analyze its logical structure. (If I’m mistaken and someone has done that, please provide a citation in the combox.) The goal of this post is to try to take first step towards filling that lacuna.

The primary source of Mackie’s argument(s) against moral realism may be found in his classic book, Ethics: Inventing Right and Wrong (Penguin, 1977). Mackie never formally states the logical structure of his argument(s). In this writer’s opinion, that omission has probably contributed to some (unnecessary and avoidable) confusion among philosophers about what his argument(s) is (are) supposed to be (and, correspondingly, what constitutes a relevant and effective refutation). But let that pass. What are his argument(s)?

A typical discussion of Mackie’s case for error theory will represent Mackie as if he had presented two arguments against moral realism: (1) the argument from relativity; and (2) the argument from queerness. But is that accurate? After re-reading his book–specifically, the conclusion of the first chapter–I’m no longer so sure about that. Here is how Mackie begins his conclusion.

I have maintained that there is a real issue about the status of values, including moral values. Moral scepticism, the denial of objective moral values, is not to be confused with any one of several first-order normative views, or with any linguistic or conceptual analysis. Indeed, ordinary moral judgments involve a claim to objectivity which both non-cognitivism and naturalist analyses fail to capture. Moral scepticism must, therefore, take the form of an error theory, admitting that a belief in objective values is built into ordinary moral thought and language, but holding that this ingrained belief is false. As such, it needs arguments to support it against ‘common sense’. But solid arguments can be found. (p. 48-9)

Then, in what has to be one of the longer run-on sentences I’ve read recently by a philosopher, Mackie summarizes those “solid arguments.”

The considerations that favour moral scepticism are: first, the relativity or variability of some important starting points of moral thinking and their apparent dependence on actual ways of life; secondly, the metaphysical peculiarity of the supposed objective values, in that they would have to be intrinsically action-guiding and motivating; thirdly, the problem of how such values could be consequential or supervenient upon natural features; fourthly, the corresponding epistemological difficulty of accounting for our knowledge of value entities or features and of their links with the features on which they would be consequential; fifthly, the possibility of explaining, in terms of several different patterns of objectification, traces of which remain in moral language and moral concepts, how even if there were no such objective values people not only might have come to suppose that there are but also might firmly persist in that belief. (p. 49)

What, precisely, does Mackie think those five solid arguments show?

These five points sum up the case for moral scepticism; but of almost equal importance are the preliminary removal of misunderstandings that often prevent this thesis from being considered fairly and explicitly, and the isolation of those items about which the moral sceptic is sceptical from many associated qualities and relations whose objective status is not in dispute. (p. 49)

So, contrary to what many metaethicists claim, I’m starting to wonder if the best interpretation of Mackie’s case against objective values is two-fold: (a) five independent supporting arguments; and (b) one main argument which somehow combine into a “case for moral scepticism.” In what follows, I’ll list what these five supporting arguments are. Since Mackie only explicitly named the first two, I’ll give my own names to the last three.

(1) The Argument from Relativity. The relativity or variability of some important starting points of moral thinking and their apparent dependence on actual ways of life.

(2) The Argument from Queerness. The metaphysical peculiarity of the supposed objective values, in that they would have to be intrinsically action-guiding and motivating.

(3) The Argument from Supervenience. The problem of how such moral values could be consequential or supervenient upon natural features.

(4) The Argument from Epistemology. The corresponding epistemological difficulty of accounting for our knowledge of value entities or features and of their links with the features on which they would be consequential.

(5) The Argument from Patterns of Objectification. The possibility of explaining, in terms of several different patterns of objectification, traces of which remain in moral language and moral concepts, how even if there were no objective values people not only might have come to suppose that there are but also might persist firmly in their belief.

Even if the rough logical structure of Mackie’s argument is the two-fold as I have suggested, the formal structure of what I’m calling the “main argument” would be a complete mystery. All Mackie says is that “These five points sum up the case for moral scepticism,” but he never explains how, in his view, that argument works. Is it an inference to the best explanation? A Bayesian-style explanatory argument? Something else? Unfortunately for us, Mackie never says.

Your thoughts?