This is the antithesis of a hand-waving opinion-piece on expressiveness. It, is, rather, a talk by Shriram Krishnamurthi introducing the key insights of Matthia

This is the antithesis of a hand-waving opinion-piece on expressiveness. It, is, rather, a talk by Shriram Krishnamurthi introducing the key insights of Matthias Felleisen's 1991 paper of the same name. From the paper's abstract: "The literature on programming languages contains an abundance of informal claims on the relative expressive power of programming languages, but there is no framework for formalizing such statements nor for deriving interesting consequences. As a first step in this direction, we develop a formal notion of expressiveness and investigate its properties. To validate the theory, we analyze some widely held beliefs about the expressive power of several extensions of functional languages. Based on these results, we believe that our system correctly captures many of the informal ideas on expressiveness, and that it constitutes a foundation for further research in this direction." Highly recommended, FWIW.