Twenty years later, Dijkstra still stood by the analogy. This time, however, he projected the lessons he had learned from programming methodology back onto mathematics. Dijkstra was thus, in 1981, keen on defining a mathematical methodology. In Dijkstra's words:
Dijkstra attended the four-day “International Symposium on Algorithmic Languages” in honor of Aad van Wijngaarden who was retiring as director of Amsterdam's `Mathematical Centre'. The symposium was held from Monday 26 October until Thursday 29 October 1981. Ershov and Turski also attended after having spent the weekend with Dijkstra at his home in Nuenen.
Toward the end of my paper `Dijkstra's Rallying Cry for Generalization ...' I briefly describe the work of Irons and Feurzeig. These two men had by 1960 also implemented ALGOL60's recursive procedure just like Dijkstra and Zonneveld. Their solution, however, was very different from the solution proposed by Dijkstra and Zonneveld.
Dijkstra's Rallying Cry for Generalization is pleased to offer to its readers Chapter III of the book Studies in Operating Systems by R. M. McKeag and R. Wilson, edited by D H. R. Huxtable and published in 1976 by Academic Press:
In his technical report (MR 34) of October 1961, Dijkstra explained why he viewed a good programming language to be one of a small number of very general concepts. To clarify, he used an analogy between mathematics and programming, an analogy which in later years would be scrutinized in several ways by his contemporaries. (See e.g. MacKenzie's 2004 book Mechanizing Proof: Computing, Risk, and Trust.)
In the late summer of 1981, Dijkstra gave several talks in Scotland and Newcastle. Here is an overview of his trip:
+ The Marine Hotel in North Berwick. The host was Mr. Hannah of Burroughs. The audience consisted of 10 men from various Burroughs plants in Europe. Dijkstra lectured for five successive days, between 6 and 7 hours per day. The "standard surprise" from the audience was that the universal quantification over the empty set yields true.
The theme of the International Summer School in Marktoberdorf was "Theoretical Foundations of Programming Methodology". The general pattern of the day was: two lectures — a break — two lectures — lunch — two lectures — break — discussion.
In his trip report, Dijkstra listed several speakers from that summer school:
Roughly 80 participants from 15 countries participated in the 1971 summer school in Marktoberdorf. According to Dijkstra, some participants were very theoretically inclined, others more practically minded. Viewed from the present day, the following list of speakers at that summer school is impressive. Dijkstra attributed a theme to each speaker, with the exception of Perlis and Dahl: