Apel, Karl-Otto (1922–)

The German philosopher Karl-Otto Apel is best known for his wide-ranging ‘transcendental pragmatic’ approach to a gamut of issues in theoretical and practical philosophy. This approach accords ‘argumentative discourse’ and its essential normative presuppositions a foundational role within all other philosophical inquiries for which justifiable validity claims are raised, for example epistemology, normative theories of rationality, Critical Theory and ethics. If there are such presuppositions then any interlocutor’s communicative intention to waive them will clash with the construal of that debate as rationally meaningful, since it involves the interlocutor in a kind of inconsistency that Apel (like Habermas), drawing on speech-act theory, conceptualizes as a ‘performative self-contradiction’. Apel (unlike Habermas) develops this concept into the doctrine of rationally definitive justification (Letztbegründung). Apel deserves to be better known as the originator of discourse ethics (Diskursethik), whose central contention (that some presuppositions of discourse have universally valid moral content) he developed in the mid-1960s.