F. Y. Edgeworth, Bertrand Russell, and Kurt Goedel come to mind. They were mathematicians, which is pretty similar. Daniel Dennett is well-acquainted with AI. Paul and Patricia Churchland are familiar with neuroscience; but I don't know how good their philosophy is. R. Penrose is good at math and physics, but not at philosophy. Wittgenstein produced some of his best insights from studying linguistics. J. Fodor is very well-educated in linguistics, and has a mixed record in philosophy (well, stuff that might be more cognitive science) of good and bad ideas. J. Searle is also well-educated in linguistics, and bad (possibly deliberately) at philosophy. Valentino Braitenberg, a roboticist, seems philosophically competent, or at least able to talk about what is likely and important in the long term.
Douglas Hofstadter started out as an AI researcher, although he now describes his work as cognitive science. Whether he's "primarily" an AI researcher, and whether his philosophy is "serious", he does seem to get a bit of respect around these areas.
This guy looks promising. I'm totally checking him out.
Opening paragraph of one of his 2008 papers:
...That correct reasoning accords with Bayesian principles is now so widely held in philosophy, psychology, computer science, and elsewhere that the contrary is beginning to seem obtuse, or at best quaint. And that rational agents should learn about the world from energies striking sensory inputs - nerves in people - seems beyond question.
I like this guy already. :)
I'm thinking of people who are primarily AI researchers, but have also done long, serious work in philosophy.
This may be unfair of me, but I can't help but think Ben Goertzel is a counterexample.
When you wrote that Judea Pearl turned significant attention to philosophy were you thinking of his work on causality or something else?
Tradition. Causality is a classic concept of philosophy, and not unique to any particular science. Many sciences just treat it as an assumption. Pearl's account of causality continues from the counterfactual accounts developed by Lewis and Stalnaker, both philosophers. But I don't really care to argue about the boundary of 'philosophy'. You could place causality under physics, maybe, or statistics.
Marcus Hutter of AIXI fame discusses the problem of induction in philosophy here (LW discussion thread).
John McCarthy has published several papers about philosophy topics (but related to AI). His Ascribing Mental Qualities to Machines always struck me as a shining example of "why we should leave philosophy to the computer scientists".
Based on a sample size of three (Pearl, Yudkowsky & Drescher), it appears that AI researchers can do quite well when they turn significant attention to philosophy. Are there other examples of this? I'm thinking of people who are primarily AI researchers, but have also done long, serious work in philosophy.