These two papers will address two 'legalising' or formalising approaches to the common good in late medieval Paris. The first will focus on Godfrey of Fontaines (c.1250-c.1306/9), not only one of the very significant thinkers on the common good in the late Middle Ages, but also, it seems, one of the first to build conceptual bridges between Aristotelian approaches to this topic and canon and Roman law. A teacher and (twice) Regent Master at the University of Paris, Godfrey also had a strong link with the College of the Sorbonne. The seminar's second part/paper will therefore look at the Sorbonne's own regulations and administrative thought about *its* collective, common good and how it sought to formalise this at a practical level. One aim of setting these two topics beside each other is to see how far, if at all, it is possible - or interesting - to see the two approaches, 'theoretical' and 'practical', as part of the same enterprise.