Res Philosophica

Volume 96, Issue 2, April 2019

Reasons and Rationality

Disagreement as Interpersonal Incoherence

In a narrow sense of ‘disagreement,’ you and I disagree iff we believe inconsistent propositions. But there are numerous cases not covered by this definition that seem to constitute disagreements in a wider sense: disagreements about what to do, disagreements in attitude, disagreements in credence, etc. This wider sense of disagreement plays an important role in metaethics and epistemology. But what is it to disagree in the wider sense? On the view I’ll defend, roughly, you and I disagree in the wide sense iff we hold attitudes that it would be incoherent for a single individual to hold. I’ll argue that this captures the relevant cases, and explore the consequences for metaethical debates between expressivists and contextualists. My view has two broader upshots: that coherence is a theoretically important property, and that an apparently descriptive question—are two subjects disagreeing?—turns on a normative one—are their attitudes jointly incoherent?