Abstract

This essay discusses a foundation of the connection argued to exist between law and practical reason that has proved to be highly influential and debated in contemporary legal philosophy – Alexy’s. After reconstructing Alexy’s conception of practical reason as well as its foundation, I criticise the weak transcendental-pragmatic argument Alexy uses to ground the authority of practical reason. This argument, I argue, can only show why occasionally, as opposed to necessarily, we ought to follow the guidance of practical reason, and consequently makes the authority of practical reason ultimately dependent on an individual decision. By building on this criticism, in the second part of the essay I introduce and discuss an alternative argument that, by appealing to the idea of constitutive necessity, can provide a non-contingent basis for the validity of practical reason