Then mathematical neatness became a goal and led to pruning some features from the core of the language. ... Another way to show that LISP was neater than Turing machines was to write a universal LISP function and show that it is briefer and more comprehensible than the description of a universal Turing machine.
— John McCarthy, History of Lisp
TL;DR Many presume the mathematical theory of functions is the sole right foundation for programming theory and languages. In contrast, Raku adopts the mathematical theory of actors (cf Scala's Akka) as its core primitive for the most demanding scenario (heterogeneous/concurrent/distributed computing), with actor=object for less demanding settings. This article drills down to that core: a metamodel ("model of a model") of a model of computation ("h