In a course we co-taught last year, we explored with students the question how to integrate insights from legal philosophy and lexical semantics (linguistics) in an interdisciplinary way. From the legal theoretical perspective, we started from Hart’s (1994) ‘persistent questions’ in which he raises philosophical problems with definitions and borderline cases (Is a stroller a vehicle?). From the linguistic perspective, we introduced prototype theory (Rosch 1973), pointing out that all psycholinguistic evidence on human cognition shows that humans do not grasp the meaning of a context by defining it (a stabbing weapon has a blade longer than 3 inches and a point), but by associating prototypical examples with the concept (a dagger is a stabbing weapon). Prototype reasoning is thus a valid alternative for definitions to grasp meaning and therefore offers a way out from Hart’s puzzle. Prototypes can be distinguished from borderline cases by exploring their semantic features (Pustejovsky 1991) (e.g. Is a kitchen knife (to peel potatoes) a stabbing weapon? It has the form and materiality of a stabbing weapon, but not its function). Finally, we presented students with such borderline legal cases. This required them to apply the prototype theory within legal philosophy reasoning (e.g. does a kitchen knife lose its function when it leaves the kitchen?), thus integrating the two disciplines. In this chapter we describe the course in more detail, introducing both theoretical perspectives and reflect upon how students dealt with the various problems we set them to solve or argue.