The new categorical imperative after Auschwitz: must morality be grounded discursively, or in the somatic moral impulse?

Theodor W. Adorno, answered from the texts and cited to the page.

The position in brief

"A new categorical imperative has been imposed by Hitler upon unfree mankind: to arrange their thoughts and actions so that Auschwitz will not repeat itself, so that nothing similar will happen again." The form of the imperative is negative: it says what must not be, not what must be; it issues from the bodily sensation of unbearable physical agony, not from the deduction of a universalizable maxim.¹

The moral impulse — the somatic recoil at suffering, the addendum (das Hinzutretende) that cannot be analytically derived from any preceding mental state — is the foundation, not discursive justification. "The need to lend a voice to suffering is a condition of all truth" (ND). "Wrong life cannot be lived rightly" (MM §18) is the diagnostic counterpart: the social form within which moral agency is supposed to operate is itself damaged in ways that contaminate every individual moral undertaking, so that morality can be approached only ex negativo, as the registration of what must not be allowed to repeat.

The determinate negation of morality — neither for nor against, both for and against — is the form: morality holds us responsible while refusing the conditions in which responsibility could be undertaken cleanly.²³

Sources

But the idea that we can say of the world as a whole in all seriousness that it has a meaning now that we have experienced Auschwitz, and witnessed a world in which that was possible and that threatens to repeat itself in another guise or a similar one - I remind you of Vietnam - to assert such an idea would seem to me to be a piece of cynical frivolity that is simply indefensible to what we might call the…
Lectures on Negative Dialectics, p. 19
The trivial consciousness, as it is theoretically expressed in positivism and unreflected nominalism, may be closer than the sublime consciousness to an adaequatio rei atque cogitationis; its sneering mockery of truth may be truer than a superior consciousness, unless the formation of a truth concept other than that of adaequatio should succeed.
Negative Dialectics, p. 365
I would say, therefore, that if metaphysical thinking today is to have any chance, and is not to degenerate into claptrap about a 'new protectedness' [neue Geborgenheit] and suchlike nonsense, it will have to cease being apologetic and pointing to something one can hold onto and never lose, and think against itself.
Metaphysics - Concept and Problems, pp. 121–122

Where the argument is made

Negative Dialectics, especially Part III 'Models' and the 'Meditations on Metaphysics' (the new categorical imperative passage, ND 365)
Minima Moralia (1951), especially §18 'Refuge for the homeless' ('there is no right life in the wrong one') and §29 'Dwarf fruit' ('the whole is the false')
Problems of Moral Philosophy (lectures 1963)
'Education after Auschwitz' (1966, in Critical Models)
the moral-impulse passages in ND

How the argument was received

The contested ground in contemporary moral philosophy that runs through Habermas-Apel discourse ethics, Honneth's recognition theory, Benhabib's interactive universalism, and the Bauman-Levinas postmodern-ethics tradition. The discourse ethicists charge that morality requires discursive grounding and that the moral-impulse foundation collapses into irrationalism. Honneth's recognition theory reads the negative-imperative form as the symptom of a defective social ontology that recognition theory remedies. Benhabib's interactive universalism attempts a version of universalism that addresses the concrete other, picking up what Habermas-Apel underspecify. Schweppenhäuser's diagnosis is that Adorno gives "no theory of universalism but only indications of its immanent dialectic" — which Schweppenhäuser reads as a feature, not a bug, but the post-Adornian critical theorists have read as the gap their constructive programs fill.