Edsger Dijkstra

There is a photograph of Edsger Dijkstra’s study that tells you almost everything before you have read a word of him. No computer. A Montblanc fountain pen and unlined paper. The man who built the intellectual foundations of the machine refused for decades to keep one in the house, and wrote the documents that shaped the field by hand, in an exquisite script, numbering them with his initials until there were more than thirteen hundred. He believed a thought worth having was a thought you could write down once, cleanly, without rewriting. His discipline was not nostalgia; it was a coherent position about what makes knowledge trustworthy. He believed a program was a mathematical object whose correctness should be demonstrable the way a theorem is demonstrable—not hoped over after testing, not inferred from performance on benchmarks, but proved from a formal specification. He gave the field its most famous algorithm—devised in