The Argument from Disagreement

The claim that the breadth and persistence of moral disagreement counts against the existence of objective moral facts.

Definition

The argument from disagreement infers from the existence of widespread, intractable moral disagreement to the conclusion that there are no objective moral facts, on the grounds that the persistence of disagreement is better explained by antirealism than by realism.

Scope

This topic examines the argument from disagreement (Mackie's 'argument from relativity') and the realist replies to it. It distinguishes the empirical premise that there is deep, persistent moral disagreement from the metaethical inference that such disagreement is best explained by the absence of objective moral facts, and it surveys realist explanations of disagreement in terms of non-moral error, partiality, and differing circumstances.

Core questions

• Is moral disagreement actually deeper or more intractable than disagreement in other domains?
• Does disagreement evidence the absence of facts, or merely the difficulty of discovering them?
• Can realists explain moral disagreement as the product of non-moral error and bias?
• What follows for moral epistemology if much disagreement is genuinely irresolvable?

Key concepts

• argument from relativity
• fundamental vs. derived disagreement
• convergence under idealization
• best-explanation reasoning

Key theories

Argument from relativity

Mackie argued that variation in moral codes is better explained as reflecting differing ways of life than as resulting from imperfect perception of objective values, supporting antirealism.

Realist error-theoretic explanation of disagreement

Realists reply that moral disagreement is explicable by non-moral disagreement, partiality, and differing background conditions, and that some convergence under idealization is observable.

History

Concerns about moral diversity trace back to ancient scepticism and to anthropological reports of divergent moral codes, but the argument received its canonical metaethical formulation in Mackie's 1977 'argument from relativity'. Brink's 1989 realist reply and later empirically informed work by Doris and Stich reframed the dispute around the best explanation of observed disagreement.

Debates

Whether disagreement is fundamental

Realists argue much apparent moral disagreement rests on differing non-moral beliefs and circumstances, so it is derived rather than fundamental; antirealists hold that at least some disagreement persists even under shared information.

What the empirical evidence shows

Empirically informed metaethics debates whether psychological and anthropological findings reveal genuinely fundamental moral disagreement or merely surface variation, with implications for both sides.

Key figures

• J. L. Mackie
• David Brink
• John Doris
• Stephen Stich

Seminal works

• mackie1977
• brink1989

Frequently asked questions

Doesn't disagreement in science also occur without making science non-objective?

This is exactly the realist's reply: scientific disagreement does not lead us to deny objective scientific facts, so the mere existence of moral disagreement need not establish antirealism unless it can be shown to be relevantly different.