Heart of Clojure

September 18 & 19, Leuven, Belgium.

The Shoulders of Giants or Uncovering the Foundational Ideas of Lisp


In the world of computer science, we often acknowledge that we are standing on the shoulders of giants. However, the identities and contributions of these giants are sometimes less known than we might expect. While many Lisp practitioners recognize John McCarthy as the inventor of Lisp, the story of the foundational ideas that enabled its discovery remains largely untold. This talk aims to explore two essential questions: Why do we know so little about the foundational ideas that enable our practice, and what are those ideas and their connections?

To answer these questions, we will embark on a journey through the foundational crisis of mathematics (Grundlagenkrise der Mathematik) that emerged at the end of the 19th century. The field was rife with paradoxes, and German mathematician David Hilbert helped sketch a plan by highlighting 23 problems. So much was at stake! For example, proving the consistency of the axioms of arithmetic, a particular form of the Entscheidungsproblem. What followed was a setback caused by Gödel’s incompleteness theorems, demonstrating the impossibility of such a proof. However, Gödel’s theory required a strict definition of computability. To that end, Gödel referred to the primitive recursive functions, the same model of computation that McCarthy would refer to in his paper, Recursive Functions of Symbolic Expressions and Their Computation by Machine, Part I. Today, Church’s lambda calculus and Turing’s machines are the better known models of computation. But all three models are equivalent. By exploring these foundational ideas and their connections, we will gain a deeper appreciation for the giants upon whose shoulders we stand and the intellectual legacy that has shaped our field.


  • Daniel Szmulewicz

    Functional programmer. Closet philosopher. Emacs meshugge.

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