What Are Thick vs Thin Moral Concepts? Explained

Direct Answer

The distinction between thick and thin moral concepts is a distinction between two kinds of evaluative vocabulary. Thin concepts — "good," "bad," "right," "wrong," "ought," "should" — are purely evaluative. They express approval or disapproval, but they carry almost no descriptive content: to call an action "good" is to evaluate it positively without saying anything much about what the action consists in. Thick concepts — "cruel," "brave," "generous," "honest," "loyal," "treacherous," "lewd," "chaste," "grateful" — combine evaluation with description. To call an act "cruel" is at once to describe it as the deliberate infliction of suffering on the vulnerable and to evaluate it negatively; to call someone "brave" is at once to describe them as acting in the face of danger and to evaluate them positively. The "thickness" consists in this fusion: the descriptive and evaluative elements are woven together in a single concept, not layered on top of each other. Thin concepts are the abstract skeleton of moral discourse; thick concepts are its flesh and blood.

Historical Context

The modern discussion of thick concepts descends from mid-twentieth-century analytic moral philosophy. The distinction is usually traced to the critique of the fact-value dichotomy mounted by philosophers in the virtue ethics tradition, especially Elizabeth Anscombe and Philippa Foot. Anscombe's famous 1958 paper "Modern Moral Philosophy" argued that the thin, obligation-laden vocabulary of modern moral theory — "ought" and "moral obligation" — is a ghost of a discarded divine-law framework, and that ethics should be rebuilt on thick concepts of virtue and vice. Foot argued that thick evaluative concepts are governed by descriptive correctness conditions, undermining the sharp separation of fact and value. The distinction was given its canonical formulation by Bernard Williams in Ethics and the Limits of Philosophy (1985), who used it to argue that moral thought is embedded in particular ways of life and is not adequately captured by abstract moral theory. Martha Nussbaum and others have since drawn on thick concepts in cross-cultural and literary ethics.

Key Arguments & Debates

The thick/thin distinction is philosophically loaded because it challenges central claims of both non-cognitivism and the fact-value distinction. Non-cognitivists hold that evaluation is added to neutral description: first we describe the facts, then we express our attitude toward them. Thick concepts seem to refute this picture: in "cruel," the description and the evaluation are not separable — there is no purely descriptive counterpart of "cruel" that leaves out the disapproval. This supports the cognitivist and realist claim that evaluative concepts can genuinely describe the world. The second debate concerns whether thick concepts are "world-guided": whether their application is constrained by the facts or is itself partly evaluative. Williams argued that thick concepts are both world-guided and action-guiding, and that they are embedded in particular cultures — which raises the question whether thick concepts can be applied across cultural boundaries. Relativists argue that they cannot, or that their application is always internal to a tradition; universalists reply that many thick concepts (cruelty, honesty, fairness) are shared across cultures. The third debate concerns the relationship between thick and thin: some philosophers argue that thin concepts are reducible to or presuppose thick ones, others that the distinction is a matter of degree rather than kind.

Contemporary Relevance

The thick/thin distinction animates several live disputes. In metaethics, it is central to the debate over moral realism: if thick concepts describe as well as evaluate, the case for moral truth is strengthened. In moral psychology and virtue ethics, thick concepts are the vocabulary in which character is assessed. In applied ethics, the choice between thick and thin vocabulary is consequential: debates about assisted dying, for example, turn on whether we describe an act as "killing" (thinly wrong) or as "mercy" (thickly informed by context). Understanding the distinction helps you see how much of moral argument is a struggle over which concepts to apply, not merely which judgments to draw.

Related Concepts

The thick/thin distinction is central to metaethics and bears on the cognitivism vs non-cognitivism debate, since thick concepts undercut the non-cognitivist separation of fact and value. It is connected to the is-ought problem and the virtue ethics tradition, whose leading figures — Anscombe, Foot, Williams, and Nussbaum — shaped the discussion.

Further Learning

The Stanford Encyclopedia of Philosophy's entry on thick ethical concepts is the authoritative survey. Bernard Williams's Ethics and the Limits of Philosophy (Fontana, 1985) contains the classic discussion, and Anscombe's "Modern Moral Philosophy" (1958) is the founding essay of the modern debate.