Apel worked in
ethics, the
philosophy of language and
human sciences. He wrote extensively in these fields, publishing mostly in German. Apel's work brings together the
analytical and
Continental philosophical traditions, especially
pragmatism and the
critical theory of the
Frankfurt School. He developed a distinctive philosophical approach which he called
transcendental pragmatics (
Transzendentalpragmatik). In
Understanding and Explanation: A Transcendental-Pragmatic Perspective, Apel reformulated the difference between understanding (
Verstehen) and explanation (
Erklärung), which originated in the
hermeneutics of
Wilhelm Dilthey and
interpretive sociology of
Max Weber, on the basis of a
Peircean-inspired transcendental-pragmatic account of language. This account of the "
lifeworld" would become an element of the theory of
communicative action and
discourse ethics, which Apel co-developed with
Jürgen Habermas. Strategic rationality both claim to stand in need of communicative rationality that is seen as, in several regards, more fundamental. While sympathetic to Habermas's
Theory of Communicative Action, Apel has been critical of aspects of Habermas's approach. Apel has proposed that a theory of communication should be grounded in the transcendental-pragmatic conditions of communication. After taking his point of departure from Apel, Habermas has moved towards a "weak
transcendentalism" that is more closely tied to empirical social inquiry. Apel also wrote works on
Charles Sanders Peirce and is a past president of the C. S. Peirce Society. An early German-speaking adversary of so-called
critical rationalism, Apel published a critique of the philosophy of
Karl Popper: In
Transformation der Philosophie (1973), Apel charged Popper with being guilty of, amongst other things, a
pragmatic contradiction. Apel died on 15 May 2017 at the age of 95. ==List of works==