Category Mistakes

Category mistakes by Dijkstra, Hoare, and others

Chapter 1 of Turing Tales

The first chapter of my 2016 book Turing Tales is made available here. I explain my methodological stance on the history of computer science, and introduce the topic of "conflations," which I believe is key to understanding the history of science and technology.

Hopcroft and Ullman


24 October 2017

Is the history of computer science solely a history of progress? I don't think so. Judge for yourself by reading the present post in which I scrutinize the famous textbooks of John E. Hopcroft and Jeffrey D. Ullman.

Quotes from 1969 and 2007

I start by comparing the following two quotes. The first quote comes from Hopcroft & Ullman, 1969:


`Plato and the Nerd,' Part 2b: Computer Science & Descriptions vs. Software Engineering & Prescriptions


23 September 2017


One of Edward A. Lee's main topics in his book, Plato and the Nerd: The Creative Partnership of Humans and Technology (MIT Press, 2017), is the contradistinction between science and descriptions on the one hand and engineering and prescriptions on the other hand. Reading between the lines, Lee is addressing the big question: Is computer science really a science?


`Plato and the Nerd,' Part 1


3 September 2017

Some computer scientists and software engineers write about the history of their fields. Others analyze and document the philosophy of their own discipline. In this latter regard, I am happy to announce the publication of Edward A. Lee's book on the philosophy of engineering:

Plato and the Nerd: The Creative Partnership of Humans and Technology (MIT Press, 2017)


Ensmenger & Flowcharts


8 July 2017

One of the questions that keeps me awake (during the day) is the following one:

What did a “computer program” mean to Actor X in 1973?

For example, both Christopher Strachey and Edsger Dijkstra viewed a “computer program” as a mathematical object, albeit of a very different kind [1]. (A decade or more earlier, both men did not associate computer programs with mathematical objects pur sang). But what about large parts of the North American computer industry in 1973? How did actors in this field view a “computer program” in 1973?


Michelle Obama vs. the Gatekeeper


15 October 2016

Category mistakes and incomputability claims seem to go hand in hand. I have given one modern example in connection with programming languages and Michael Hicks and another one directly concerning the diagonal argument. In the present blog post I shall give one more example, based on an excerpt from my rejected POPL paper entitled: `Category Mistakes in Computer Science at Large.' Specifically, I shall zoom in on the “code improvement problem,” as discussed by Albert R. Meyer and Dennis M.



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