From the cover of his first book, Robert Alexy has been using the terms discourse and argumentation synonymously. Despite this pattern of usage, he (Alexy, 1989, p. 180) favors the word discourse, as he names his theory of argumentation a theory of discourse. Alexy (1989, p. 180) further classifies his theory as normative because it does not aim to describe the rules of argumentation actually employed by specific individuals, but rather to prescribe the rules that make discourses rational.
Discourse, according to Alexy (1989, p. 179), is a set of interconnected actions in which participants use arguments to prove the truth of empirical propositions or the correctness of normative propositions. Empirical propositions refer to facts, and normative propositions encompass both value judgments and norms that obligate, permit, or prohibit certain actions.
He (Alexy, 1989, p. 179 and 206) labels discourses about empirical propositions as theoretical and discourses about normative propositions in general as practical. I believe that these normative propositions can be divided into two kinds: a) legal; b) and non-legal. In turn, non-legal normative propositions are subdivided by Alexy (1996, p. 1033; 2015, p. 134) into three types.
The first type of non-legal normative propositions aims to regulate the actions of all human beings in a fair manner, the second aims to regulate how people establish life projects for themselves, and the third intends to regulate the search for the best means to achieve certain ends (Habermas, 1994, p. 1-17).
Legal discourse is categorized by Alexy as a special case of general practical discourse because it also seeks to justify the correctness of normative propositions; however, this justification is limited by legislation, legal doctrine, and judicial precedents (Alexy, 1989, p. 179-180).
Alexy (1989, p. 179) argues that the rationality of discourses depends on compliance not only with logical rules, but also with rules of conduct by participants during argumentation, and adds that such obedience does not guarantee the definitive certainty of all discourse outcomes, but qualifies these outcomes as rational.
Bibliographic references
ALEXY, Robert. A teoria do discurso jurídico de Jürgen Habermas. In: ALEXY, Robert. Direito, Razão, Discurso: Estudos para a filosofia do direito. Translated and revised by Luís Afonso Heck. 2nd ed. rev. Porto Alegre: Livraria do Advogado Editora, 2015. p. 128-135.
ALEXY, Robert. Jurgen Habermas’s Theory of Legal Discourse. Cardozo Law Review, Vol. 17, Iss. 4-5, 1996. p. 1027-1034. Available at: https://larc.cardozo.yu.edu/clr/vol17/iss4/12. Acessed on: 21 feb. 2026.
ALEXY, Robert. A Theory of Legal Argumentation: The Theory of Rational Discourse as Theory of Legal Justification. Translated by Ruth Adler and Neil MacCormick. 1st ed. New York: Oxford University Press, 1989.
HABERMAS, Jürgen. On the Pragmatic, the Ethical, and the Moral Employments of Practical Reason. In: HABERMAS, Jürgen. Justification and Application: Remarks on Discourse Ethics. Translated by Ciaran Cronin. 1st ed. Massachusetts: MIT Press, 1994. p. 1-17.