I’m writing a book about epistemology. It’s about The Problem of the Criterion, why it’s important, and what it has to tell us about how we approach knowing the truth.
I’ve also written a lot about AI safety. Some of the more interesting stuff can be found at the site of my currently-dormant AI safety org, PAISRI.
For me this is a tough question since I’ve been reading your stuff for nearly 10 years now, but thinking of only OB I’d have to say it was the quantum physics stuff, but only because I had encountered essentially everything else in one form or another already, so your writing was just refining the way of presenting what I had already generally learned from you.