Karl-Otto Apel

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Karl-Otto Apel (born March 15, 1922 in Düsseldorf ; † May 15, 2017 in Niedernhausen ) was a German philosopher . He was a representative of discourse ethics and a language-pragmatic, intersubjective transcendental philosophy or transcendental pragmatics . Apel aimed for a "transformation of philosophy". The exit from the subject must be overcome in favor of an intersubjective perspective without losing the insights gained by Immanuel Kant in the inevitable constitutional conditions of objectivity .

The main intention of Apel was to defend against relativistic positions, especially in ethics . Together with his colleague Jürgen Habermas , who had been a friend since his student days , Apel attempted to reformulate Kantian moral theory with a view to the question of the justification of norms using means of communication theory.

Life and thought path

Apel grew up during the political crises of the Weimar Republic. In 1940 he became a war volunteer with his entire high school class. After the Second World War, Apel first studied history and intellectual history at the Rheinische Friedrich-Wilhelms-Universität Bonn from 1945 to 1950 , before settling on philosophy as a student of Erich Rothacker .

In 1950 he received his doctorate in Bonn with a thesis on Heidegger , in 1961 he completed his habilitation in Mainz on the humanistic idea of ​​language (the idea of ​​language in the tradition of humanism from Dante to Vico) . From 1962 to 1969 he was full professor for philosophy at the Christian-Albrechts-Universität zu Kiel , from 1969 to 1972 full professor for philosophy at the University of Saarbrücken and from 1972 until his retirement in 1990 full professor for philosophy at the University of Frankfurt on the Main .

As a basic experience of his early student years - which was decisive for his later philosophical career - Apel describes the "dull feeling" that "everything was wrong, for which we had campaigned". The intellectual offer that was available during the period of reconstruction (Dilthey, Heidegger) could not answer the questions that preoccupied him.

Nevertheless, a non-political phase initially followed in Apel's biography. He dealt with existential philosophy out of “defiant indifference to the political and historical shadows of the recent past” , since it was not about “what one had campaigned for, but how one had done it”. In 1950 he received his doctorate in Bonn with a work on Heidegger Dasein and Recognition, which was never published as a book . An epistemological interpretation of the philosophy of M. Heidegger . His writing The Idea of ​​Language in the Tradition of Humanism from Dante to Vico , with which he completed his habilitation in Mainz in 1961, was still moving along the lines of hermeneutic philosophy. This work is now regarded as a standard work on the history of the philosophy of language.

Although Apel had been grappling with analytical philosophy since the late 1950s, it was not until the 1960s that he began to break away from hermeneutics using its means. Apel has the merit of mediating between the most influential currents of philosophy at the time. Above all, the relationship between Heidegger and Wittgenstein was subject to extensive studies. In particular, Apel focused on the problem of the relationship between the natural sciences and the humanities and their methodologies, " explaining and understanding ".

For Apel, the late 1960s meant a “politically emancipatory awakening period”. An intensive examination of political philosophy began , especially the young Marx , western neo-Marxism , and critical theory . He was strongly influenced by his former fellow student in Bonn, Jürgen Habermas . He was critical of the student movement because he saw in it a misunderstanding of democratic and constitutional thinking and the danger of a utopian loss of reality. Nevertheless, he attested to her that she had forced the breakthrough into public discussion of the political situation, which was overdue for the post-war situation, and had created a political-philosophical awareness.

In the discourse climate that was emerging during this period, Apel began to develop his main work, Transformation of Philosophy . In connection with his studies of Wittgenstein and Heidegger, Apel recognized intersubjectivity as a great shared discovery. However, since these approaches appeared to him to be inconsistent, Apel has been involved in transcendental questions since the late 1960s, which he sought to convey with the intersubjectivity approach. At the same time there was an intensive discussion with Charles Sanders Peirce , of whose writings he published a selection in German translation in 1967 and 1970 with extensive introductions. Starting from Peirce's consensus theory of truth and the foundation of ethics based on it, Apel came to the view that the prerequisite for all knowledge is not the lonely subject, but always the human communication community. On this basis, Apel has been developing his "Transcendental Pragmatics" since the early 1970s with the aim of moving from the traditional philosophy of individual consciousness and the subject to a philosophy of intersubjective understanding.

Karl-Otto Apel died in May 2017 at the age of 95.


Hermeneutics and language criticism

Apel can be regarded as one of the first German philosophers who combined the previously separate and contradicting currents of Heidegger's hermeneutic philosophy and language-analytical philosophy in the wake of Wittgenstein. By criticizing Heidegger, whom he accuses of forgetting the logos, and of the early Wittgenstein, whose Tractatus he regards as a self-contradicting delimitation of reason, Apel tries to grasp not only the differences but also the similarities between the two currents. Both Heidegger's and Wittgenstein's philosophy are characterized by overcoming or 'twisting' metaphysics . Both directions are aimed at the pragmatic life world, as Heidegger by the primacy of the handiness of the theoretical extantness is expressed. Wittgenstein's analysis of language games also goes in this direction . Since pragmatics and language as an intersubjective structure play a central role in both thinkers, the transition to the philosophy of the present as the philosophy of intersubjectivity is complete in both cases. Starting from an examination of these two philosophical directions, Apel tries in his transcendental hermeneutics to mediate between the models of explaining the world in the natural sciences and the understanding of the world in the humanities .

Intersubjectivity and reflexivity

Apel sees it as the great achievement of 20th century philosophy to have overcome methodical solipsism , which in his eyes had characterized the whole of modern philosophy from Descartes to German idealism . The solipsistic conviction that "in principle 'one person' alone 'could recognize something as something and thus pursue science" was rightly rejected by Wittgenstein and Heidegger. The positive downside of this rejection is the orientation towards language, which after the pre-Kantian ontology and the transcendental philosophy of consciousness introduced linguistically mediated intersubjectivity as the third paradigm of Western philosophy. According to Apel, however, these approaches get entangled in contradictions due to their prohibition of reflexivity, which endanger their binding nature. Without breaking this prohibition, intersubjective understanding and ultimate justification would be impossible.

Speech acts

A milestone in the development of transcendental pragmatics was Apel's examination of the speech act theory of Austin and Searle. The most important achievement of speech act theory is Apel's discovery of the performative-propositional double structure of human speech. Sentences can only be expressed in speech acts, which therefore constitute the fundamental unit of human language. With each speech act four validity claims are made: intelligibility of the utterance, truth of its propositional component, correctness of its performative component and truthfulness of the speaking subject, which Apel interprets as the intersubjective dimension of every speech act.

Forms of rationality

In his work, Apel differentiated between various forms of rationality, although the individual structures and terms differ somewhat. The individual forms of rationality represent different but related moments in the apprehension of reality.

An early thesis of Apel is that human knowledge is bound to the body, which he calls "Leibapriori". Corporeality and consciousness complement each other for Apel; Both together form complementary a priori elements for human cognition: "In principle, cognition can no longer be separated from acting intervention in the world, and therein lies the abolition of the Cartesian subject-object separation."

In his work The “Explanation: Understanding” controversy in a transcendental-pragmatic perspective , he assumes four forms of rationality: a “scientific”, “technological”, “hermeneutic” and “ethical” rationality. Apel is primarily concerned with the relationship between explaining and understanding scientific or hermeneutic rationality. Both forms of rationality refer, on the one hand, to different areas of reality: that which is scientifically explained by specifying effective causes cannot at the same time be understood as an expression of an intention. Both forms of rationality also complement each other: hermeneutic understanding requires explanatory knowledge, while conversely a scientific explanation is only possible if the researchers involved understand and recognize each other as subjects with intentions.

In a later essay, Apel then differentiates between a “formal-logical” and a “transcendental rationality” in the context of the problem of ultimate justification. While the former is measured by the syntactic-semantic consistency of propositional sentences, the latter is about the "pragmatic consistency of speech acts or of performative-propositional sentences which make the 'double structure' of speech acts explicit". The distinction between a formal-logical (or mathematical) and a transcendental type of rationality corresponds, according to Apel, to the traditional distinction between understanding and reason. While formal-logical rationality explains the behavior of objects in a scientific way, transcendental or discourse rationality is about the understanding of subjects.

Ultimate reason

Apel's final justification argument arose as a reaction to the Münchhausen Trilemma first set up by Hans Albert in 1968 , according to which final justifications are not possible. For Apel, the search for the last, independent of common sense reasons had become inevitable in view of the abuse of the argumentation figure of the “ healthy people's feeling ” under National Socialism.

For Apel, the ultimate philosophical justification consists in the demonstration that certain statements must always be presupposed in any argument by each individual, regardless of what special opinion, worldview or culture he represents. Apel formulated two criteria that should identify sentences as the ultimate justification:

  • They cannot be disputed “without pragmatic self-contradiction”
  • They cannot be justified “ without a logical circle ( petitio principii ) (formal-logical)”

Apel cited as an example of pragmatic inconsistent sentences: "I am claiming that I do not exist", "I am claiming that I have no meaningful claim", "I am claiming that I have no claim to truth". The impossibility of a circle-free logical justification does not indicate an aporia in the problem of justification in these sentences, but is "a necessary consequence of the fact that the sentences are a priori certain as recognizable necessary presuppositions of all logical justification".

Apel often referred to the type of contradiction he analyzed as a performative contradiction . It does not come from subjective thinking, but from the act of intersubjective conversation, so that for Apel intersubjectivity results as an inevitable determination of human thought and action.

Discourse ethics

With this “ultimate justification criterion”, Apel defended fundamental discourse norms and developed a discourse ethics as represented by Jürgen Habermas in a weakened form - that is, without any final justification claim. He developed the ethical principles from the assumptions that, according to his conviction, have always been presupposed in any discussion of any ethics, including ethical nihilism . Every philosophical and ethical approach appeals to the criterion of the objective liability and truth of one's own statement, so that the requirement of liability and truthfulness according to Apel cannot reasonably be called into question. Apel's aim was to defend himself against ethical nihilism and to return to an objective and rational ethic that aims to overcome the “paradox” of the present. He saw the separation between objective factual knowledge of the individual sciences and the privacy and arbitrariness of ethical convictions as one of the main problems of modernity, from which discourse ethics should represent a way out.

The a priori of the argument

The central concern of Apel's discourse ethics is the ultimate justification of the ethical principles that are already implicitly presupposed with every argument, indeed with every meaningful action in general. To this end, he sought a “transformation of the Kantian position” in the direction of a “ transcendental theory of intersubjectivity ”. From this transformation he hoped for a unified philosophical theory that could bridge the contradiction between theoretical and practical philosophy.

In Apel's view, anyone who argues always assumes that he can arrive at true results in the discourse, that is, that truth is fundamentally possible. The person making the argument presupposes the same capacity for truth from his interlocutor with whom he enters the discourse. In Apels' language, this means that the argumentation situation cannot be evaded by anyone who argues. Every attempt to escape it, for example by lying or by refusing to discourse, is ultimately consistent . In this context, Apel speaks of an "a priori of argumentation":

"Whoever takes part in philosophical argumentation at all has already implicitly recognized the preconditions just indicated as a priori of argumentation, and he cannot deny them without at the same time disputing argumentative competence" . According to Apels, even those who break off the argument want to express something:
"Even those who, in the name of existential doubts that can verify themselves through suicide ... declare the a priori of the mutual understanding community to be an illusion, at the same time confirm it by still arguing . "

Someone who wants to forego an argumentative justification of his action ultimately destroys himself. In theological terms one could therefore say that even “the devil can only be made independent of God through the act of self-destruction” .

Real and ideal communication community

According to Apel, with the inevitability of rational argumentation, a community of argumentators is also recognized. The justification of a statement is not possible "without in principle assuming a community of thinkers who are capable of understanding and building consensus." Even the de facto lonely thinker can only explain and check his arguments insofar as he is in the critical 'conversation of the soul with oneself '(Plato) is able to internalize the dialogue of a potential argumentative community. This presupposes, however, the observance of the moral norm that all members of the argumentation community recognize each other as equal discussion partners.

This community of arguments, which must be assumed, comes into play in two ways at Apel:

  • as a real communication community, of which you “have become a member yourself through a socialization process”.
  • as an ideal communication community "which in principle is able to adequately understand the meaning of its arguments and to definitely judge their truth"

From the necessary presupposed communication community in its two variants, Apel derived two regulative principles of ethics:

“Firstly, everything must be about ensuring the survival of the human species as the real communication community, and secondly about realizing the ideal communication community in the real one. The first goal is the necessary condition of the second goal; and the second goal gives the first its meaning - the meaning that is already anticipated with every argument. "

According to Apel, both the ideal and the real communication community must be demanded a priori. The ideal and real communication community are in a dialectical context. The possibility of overcoming their contradiction is to be assumed a priori. The ideal communication community, as the goal to be worked towards, is already present in the real communication community as its possibility.

Complementary principles

Apel saw the problem that the high demands of his discourse ethics can only be realized in a society that is itself organized discursively. As long as it is not, these can and should also be implemented with non-discursive means. However, according to Apel, the end does not justify the means. Rather, in the process of progressive realization of the “ideal communication community”, “supplementary principles” must be drawn up that limit the scope of the permitted means. So it could be B. not be allowed to endanger the already existing forms of discourse such as parliamentary democracy for the purpose of realizing ideal discourse conditions: "The burden of proof for risky reforms or even intentional revolutions would indeed be on the part of the innovators."

Conventional and post-conventional morality

In his analysis of the problem of implementing moral norms and the conditions for their failure, as in the time of National Socialism , Apel resorted to the moral theory of Lawrence Kohlberg . Kohlberg had a preconventional, conventional and postconventional described level of moral development with a total of six stages. Each of these stages has - corresponding to the logical stages of the thought operations in Piaget - a new logical structure, which can also be understood as a “structure of justice”. According to Apel, moral development is associated with a change in the social role assumed in each case ("role taking") and "reciprocity thinking":

level step Moral orientation
Preconventional level 1: Penalty orientation No reciprocity thinking yet, no “role taking”;
Orientation of the action to the possibly associated penalty
2: Naive strategic conception of justice Fair exchange of specific services between two people
Conventional level 3: Reflected "role taking" Treatment of the other as one would like to be treated;
Restriction to specific reference groups (family, friends, acquaintances);
no specification of the role obligations
4: “Law and Order” perspective Treatment of the other as one would like to be treated;
No restriction to a specific reference group, but reference to the social system;
Role obligations are specified
Post-conventional level 5: Perspective of the "lawmaker" (legalistic contract orientation) Reference to the natural right of individuals to justify the social order through contracts from the point of view of utility and, if necessary, to change it;
Overcoming the group or state-related point of view through the idea of ​​the freedom of all people
6: "Moral point of view" Orientation towards universal ethical principles;
Demand for complete reversibility of "role taking"

Apel interpreted the moral catastrophe of National Socialism as an "adolescent crisis of humanity" in the transition from the conventional to the post-conventional level of morality. On the one hand, the social rules are no longer recognized as binding, on the other hand, the individual does not yet feel any obligation to justify his decisions with principles that are to be brought into harmony with the interests of society. Essentially responsible for this crisis for Apel were the philosophy of Friedrich Nietzsche and Martin Heidegger, which led to a “paralysis of the ethical awareness of principles” and “together with a compensative nationalism [...] had resulted in the failure of the 'intellectual elite' in the Third Reich ".


In the 1970s to 1990s, Apel was one of the most influential German philosophers, especially because of his "transcendental language pragmatics", which was intended as a critical renewal of the Kantian transcendental philosophy . His ethics of discourse sparked lively controversy in the last decades of the 20th century. His arguments with Odo Marquard , Hermann Lübbe , Hans Albert , Richard Rorty , Jacques Derrida and Jean-François Lyotard caused a stir . Apel's most important students include Dietrich Böhler , Matthias Kettner and Wolfgang Kuhlmann .


A major objection to concepts of ultimate justification as advocated by Apel is based on the difficulty of evaluating sentences regardless of their context. This is opposed by several standpoints represented in philosophy. For example, the Duhem-Quine thesis explicitly states that sentences are never evaluated in isolation, or, according to Thomas S. Kuhn , theories always include (partly unconscious) basic assumptions that are important for the interpretation and evaluation of the individual sentences.

Especially representatives of critical rationalism such as Hans Albert (treatise on critical reason) pointed to the logical impossibility of such an ultimate justification, for example by referring to the Münchhausen trilemma . Apel defended his argument by stating that the ultimate justification is not a deductive form of justification or proof, but a reflection on the conditions of the possibility of discourse in general.

Apel was also accused that his argumentation was only valid for those who already had the will to discuss: “All the tacit implications of the discourse that Apel reflexively reveals only apply if you want to argue , i.e. if you want to be rational wants. ” Apel could therefore not justify a universal ethics , that is to say valid for all people.

Another point of criticism concerns the question of the motivation for moral action. Even if Apel could have inevitable norms for the discourse, it would remain unclear why one would have to adhere to these norms willingly.


  • The idea of ​​language in the tradition of humanism from Dante to Vico . Bouvier, Bonn, 1963. 3rd edition 1980, ISBN 3-416-01089-2
  • Transformation of Philosophy , Suhrkamp, ​​Frankfurt am Main, 1973. 2 volumes
    1. - Language analysis, semiotics, hermeneutics , ISBN 3-518-27764-2
    2. - The Apriori of the Communication Society , ISBN 3-518-27765-0
  • Charles S. Peirce's Path of Thought. An Introduction to American Pragmatism , Suhrkamp, ​​Frankfurt 1975, ISBN 978-3-518-07741-2
  • The explanations: Understanding controversy in a transcendental-pragmatic view , Suhrkamp, ​​Frankfurt am Main, 1979, ISBN 3-518-06109-7
  • Discourse and responsibility. The problem of the transition to post-conventional morality , Suhrkamp, ​​Frankfurt am Main, 1988, ISBN 3-518-28493-2
  • Debates in testing the transcendental-pragmatic approach , Suhrkamp, ​​Frankfurt am Main, 1998, ISBN 3-518-58260-7
  • Paradigms of the First Philosophy: On the reflexive - transcendentally pragmatic - reconstruction of the history of philosophy , Suhrkamp, ​​Frankfurt 2011, ISBN 978-3-518-29585-4
  • Transcendental Reflection and History , edited and with an afterword by Smail Rapic, Suhrkamp, ​​Berlin 2017, ISBN 978-3-518-29814-5 .


  • Eva Buddeberg: Responsibility in Discourse. Basic lines of a reconstructive-hermeneutic conception of moral responsibility following Hans Jonas , Karl-Otto Apel and Emmanuel Lévinas . De Gruyter, Berlin 2011, ISBN 978-3-11-025146-3 .
  • Stefan Drees: Discourse and Liberation Ethics in Dialog. A case study on the sociology of the philosophers. Wissenschaftsverlag Mainz, Aachen 2002, ISBN 3-86073-935-2 .
  • Vittorio Hösle : The crisis of the present and the responsibility of philosophy. Transcendental pragmatics, ultimate justification, ethics . CH Beck, Munich 1990, ISBN 3-406-34757-6 .
  • Klaus Oehler : Is a transcendental justification of semiotics possible? In: Klaus Oehler (Ed.): Signs and Reality. Stauffenburg, Tübingen 1984, Vol. 1, pp. 45-59, ISBN 3-923721-81-1 .
  • Smail Rapic: Normativity and History. About the dispute between Apel and Habermas . Alber, Freiburg 2019, ISBN 978-3-495-49019-8 .
  • Walter Reese-Schäfer : Karl-Otto Apel for an introduction. With an afterword by Jürgen Habermas. Junius, Hamburg 1990, ISBN 3-88506-861-3 .
  • Gerhard Schönrich: Discourse on occasion. On the limits of discourse ethics and the price of ultimate justification . Suhrkamp, ​​Frankfurt am Main 1994, ISBN 3-518-28711-7 .
  • Uwe Steinhoff: Critique of communicative rationality. A presentation and criticism of the philosophy of communication theory by Jürgen Habermas and Karl-Otto Apel . Mentis, Paderborn 2006, ISBN 3-89785-473-2 .
  • Günther Witzany : Transcendental pragmatics and e-sistence. Justification of standards - enforcement of standards . Verlag Die Blaue Eule, Essen 1991. ISBN 3-89206-317-6 .

Web links


  1. Philosopher Karl-Otto Apel died. In: ORF.at . Österreichischer Rundfunk , May 16, 2017, accessed on May 16, 2017 .
  2. Andreas Dorschel (Ed.), Transzendentalpragmatik , Suhrkamp, ​​Frankfurt am Main 1993. [1] (PDF; 319 kB).
  3. This is the title of his main work, a collection of essays published in 1973.
  4. On the biography of Apels cf. Vittorio Hösle: The crisis of the present and the responsibility of philosophy , pp. 110–115; Walter Reese Reese-Schäfer: Karl-Otto Apel for an introduction , pp. 15–21.
  5. Apel: Discourse and Responsibility , p. 374.
  6. Apel: Discourse and Responsibility , p. 377.
  7. Vittorio Hösle: The crisis of the present and the responsibility of philosophy , p. 112.
  8. Apel: Discourse and Responsibility , p. 378.
  9. Apel: Discourse and Responsibility , p. 379.
  10. Vittorio Hösle: The crisis of the present and the responsibility of philosophy , p. 114.
  11. Apel: Language . In: Hermann Krings, Hand Michael Baumgartner, Christoph Wild (Hrsg.): Handbook of Philosophical Basic Concepts . tape 5 . Kösel Verlag, Munich 1974, ISBN 3-466-40059-7 , p. 1383-1402 .
  12. Apel: The communication community as a transcendental requirement of the social sciences (1972), in: Transformation der Philosophie , Vol. 2, pp. 220–263, here p. 234.
  13. Apel: The communication community as a transcendental requirement of the social sciences , p. 237.
  14. Apel: Das Leibapriori der Wissens , in: Archive for Philosophy , Vol. 12, Issue 1–2, 1963, pp. 152–172. Improved reprint in: Hans-Georg Gadamer , Paul Vogler (ed.): Neue Anthropologie , Vol. 7, G. Thieme, Stuttgart 1974 and dtv, Munich 1975, pp. 264–288.
  15. Apel: The body priority of knowledge , p. 280.
  16. Apel: The “Explanation: Understanding” controversy in a transcendental-pragmatic view (1979), p. 27.
  17. Apel: The problem of a philosophical theory of the types of rationality , in: Herbert Schnädelbach (Ed.): Rationality, Philosophical Contributions , Frankfurt a. M. 1984, pp. 15-31, here p. 23.
  18. Apel: Rationality Criteria and Rationality Types. Attempt at a transcendentally pragmatic reconstruction of the difference between understanding and reason , in: Axel Wüstehube (Hrsg.): Pragmatische Rationalitätstheorien . Königshausen & Neumann, Würzburg 1995, pp. 29-64.
  19. Hans Albert: Treatise on Critical Reason . Mohr Siebeck, Tübingen 1968, 5th verb. & exp. Edition 1991, ISBN 3-16-145721-8 , as UTB 1992: ISBN 3-8252-1609-8 .
  20. See Apel: Discourse and Responsibility , p. 409.
  21. a b Apel: The Problem of a Philosophical Theory of Rationality Types , p. 24.
  22. a b cf. Apel: The a priori of the communication community . In: Transformation der Philosophie , Vol. 2, pp. 358–435, here p. 414.
  23. a b Apel: Transformation of Philosophy . Vol. 1, p. 62.
  24. Apel: The a priori of the communication community . In: Transformation of Philosophy . Vol. 2, pp. 358-435, here p. 399.
  25. a b Apel: The a priori of the communication community . In: Transformation of Philosophy . Vol. 2, pp. 358-435, here p. 429.
  26. Apel: The a priori of the communication community . In: Transformation of Philosophy . Vol. 2, pp. 358-435, here p. 431.
  27. Apel: Discourse and Responsibility, p. 468.
  28. Apel: Discourse and Responsibility, p. 317.
  29. a b Apel: Discourse and Responsibility, p. 410.
  30. Apel: Fallibilism, consensus theory of truth and ultimate justification . In: Forum for Philosophy Bad Homburg (Hrsg.): Philosophy and justification . Suhrkamp, ​​Frankfurt am Main pp. 116–211 (extended version in Apel: Confrontations. In testing the transcendental-pragmatic approach . Suhrkamp, ​​Frankfurt am Main 1998).
  31. Walter Reese-Schäfer: Border gods of morality . Suhrkamp, ​​Frankfurt am Main 1997, p. 73.