Why should we act morally? This question regarding justification has like no other occupied
moral philosophy since the Second World War. Eventually a perspective has prevailed that has
abandoned traditional models of justification in favour of ethical pluralism and moral
progress. Since there should no longer be any external reasons only that which can be thought
without contradiction can be considered generally binding. But what does contradiction mean
here? This study brings Wittgenstein's philosophy of language into constellation with critical
theory in order to show that modern moral philosophy must fail because of its claim. The
starting point is Wittgenstein's private language argument and in particular §125 of the
Philosophical Investigations in which he describes contradiction as the central philosophical
problem of bourgeois society. It becomes clear that neither freedom from contradiction nor
moral justification precede social practice. On the contrary the supposed rationality of
modern moral philosophy reflects the contradictions of our society. The task of philosophy is
therefore not to resolve these contradictions but to expose them through critical linguistic
analysis. By bringing Wittgenstein into dialogue with Marx Adorno and Horkheimer a new
approach to moral philosophy emerges - a critique that is both linguistic and social.
