This all started with a simple question about the R programming language: is R lexically or dynamically scoped?

To answer that question, we need to understand what scope is, along with lexical scope and dynamic scope.

From the PRL archives:

I think that I shall never see a matrix lovely as a tree. — Trees, by Guy L. Steele Jr., MIT, 1973

From the PRL archives:

It was also a concept that grabbed my mind, ran off with it, and only returned it after substantial renovation and expansion. — Continuations by Alan Nall, Indiana University, 1983

“Meaningful distinctions deserve to be maintained.” — Errett A. Bishop

Likewise, memorable quotations deserve to be read in context. In this spirit, I am happy to present the above “basic principle” in its context: Schizophrenia in contemporary mathematics (pdf)

Read on for a brief summary.

Christos Dimoulas is currently teaching a “History of Programming Languages” class at Harvard. The class is, as Christos writes, “definitely not about this”; instead, each meeting is a deep examination of a single, mature research topic, in terms of three to five key papers from the literature.

On Monday, I presented “the History of Actors” for the class. I’ve made the written-out talk notes and an annotated bibliography available here.