  Habermas's encounter with speech act theory proved to be particularly decisive for this project. In speech act theory, he finds the basis for a conception of communicative competence (on the model of Chomsky's linguistic competence). Given this emphasis on language, Habermas is often said to have taken a kind of “linguistic turn” in this period. He framed his first essays on formal pragmatics (1976ab) as an alternative to Niklas Luhmann's systems theory. Habermas understands formal pragmatics as one of the “reconstructive sciences,” which aim to render theoretically explicit the intuitive, pretheoretical know-how underlying such basic human competences as speaking and understanding, judging and acting. Unlike Kant's transcendental analysis of the conditions of rationality, reconstructive sciences yield knowledge that is not necessary but hypothetical, not a priori but empirical, not certain but fallible. They are nevertheless directed to invariant structures and conditions and raise universal, but defeasible claims to an account of practical reason.