What are thick concepts?

Bernard Williams, answered from the texts and cited to the page.

Bernard Williams answers

Thick ethical concepts are those in which fact and value are inextricably intertwined — neither a bare description with a flag of disapproval attached, nor a pure evaluation floating free of any factual content.¹ Take infidelity. If I accuse you of being unfaithful, I thereby censure you; but I also say something I am obliged to retract if it turns out that you have not in fact gone back on any relevant agreement.²

The concept does both things at once, and the two aspects cannot be cleanly separated without losing the concept itself. Contrast these with thin ethical concepts — good, right, wrong, ought — which are the terms that exclusively interest the ethical theorists.³ The thin concepts have shed the descriptive content that gave the thick ones their grip; what remains is evaluative force without the factual texture that made evaluation possible in the first place.

The morality system, with its preference for thin and general terms, has performed a kind of impoverishment on our ethical vocabulary without noticing what was lost. The examples accumulate readily: treachery, cowardice, cruelty, chastity, courage, sloth, brutality, pride.⁴ What they share is that one cannot apply them correctly without knowing something about the situation — they are subject to factual correction — and yet applying them is already to evaluate, not merely to describe.

The question of whether someone was treacherous is not answered by first establishing the facts and then adding a verdict; the concept carries the verdict in its descriptive content. One further consequence is that convergence in the use of thick concepts can constitute genuine knowledge.⁵ When a community shares these concepts and converges in applying them, that convergence is not merely agreement in attitude; it tracks something about the world.

This is precisely where thick concepts differ from the thin ones, and it is why the reduction of ethics to thin concepts is not a refinement but a loss.

Sources

1. fact and value are inextricably intertwined in them. This is one reason why the language in which they are couched gives such a poor indication of the underlying metaphysics.

   Ethics and the Limits of Philosophy, pp. 215–216

2. If I accuse you of being unfaithful, I thereby censure you; but I also say something that I am obliged to retract if it turns out that you have not in fact gone back on any relevant agreement.

   Philosophy as a Humanistic Discipline, p. xvi

3. it is the thin terms, by contrast, that exclusively interest the ethical theorists.

   Essays and Reviews 1959-2002, p. 314

4. the importance of 'thick' ethical concepts, such as treachery or lie or cowardice, as contrasted with thin and general terms such as good and right

   Essays and Reviews 1959-2002, p. 314

5. People sometimes converge in their ethical beliefs, and those beliefs sometimes constitute knowledge. This can happen precisely when the beliefs in question involve a thick ethical concept.

   Philosophy as a Humanistic Discipline, p. xvi