It has been frequently remarked that the works of Robert Alexy form a system. Mattias Kumm compares Alexy's work to Dworkin's and claims that ‘their works exhibit a holistic or system-based approach to the study of law’. Pavlakos praises Alexy for having developed ‘a systematic philosophy covering most of the key areas of legal philosophy’. With an eye to links between his main works, Robert Alexy himself has remarked that ‘the result may well be a system’. How this system should be explicated, however, has not been addressed in an effective way. This, essentially, is the main aim of this chapter. It begins with an overview of Alexy's main works. The overview reflects the three pillars of Alexy's work, along the lines of his three main monographs and the most important articles. These are Alexy's doctoral thesis, A Theory of Legal Argumentation; his ‘Habilitation’ thesis, A Theory of Constitutional Rights; and The Argument from Injustice. The relations and interconnections between and among the three pillars are identified. These first steps serve to collect and analyse the material and to prepare the way for the last step, which focuses on the system as a whole.