The confusion is possibly almost appropriate, given so much of his work was on creating systems which avoid confusion through using proper synchronized communication channels. The null pointer stuff is famous, but it's occam and the Communicating Sequential Processes work that were brilliant. Maybe it's also brilliantly wrong, as I think Actor model people could argue, but it is brilliant.

My favourite quote of his is “There are two ways of constructing a piece of software: One is to make it so simple that there are obviously no errors, and the other is to make it so complicated that there are no obvious errors.”

While we hope it's not true, if it is a very deserved RIP.

CSP and Hoare logic were brilliant. He was a huge proponent of formal methods.

He famously gave up on making formal methods mainstream, but I believe there will be a comeback quite soon.

On generated code, verification is the bottleneck. He was right, just too early.

(btw the "confusion" here was confusion about whether he had actually died. this comment was originally posted to https://news.ycombinator.com/item?id=47316880, which was the thread we merged hither)

And here we are throwing all that brilliance away with Async abominations. Software can be so simple and elegant.

Actor model would also be brilliantly wrong: it doesn't compose smaller correct systems into larger correct systems.

(Software) Transactional Memory and other ideas inspired by databases have a much better shot at this.