My main research interest lies in mathematical and philosophical logic, particularly set theory, with a focus on the mathematics and philosophy of the infinite. I have worked particularly with forcing and large cardinals, those strong axioms of infinity, and have investigated the interaction of these two central set-theoretic concepts. I have worked in the theory of infinitary computability, introducing (with A. Lewis and J. Kidder) the theory of infinite time Turing machines, as well as in the theory of infinitary utilitarianism and, more recently, infinite chess. My work on the automorphism tower problem lies at the intersection of group theory and set theory. Recently, I am preoccupied with various mathematical and philosophical issues surrounding the set-theoretic multiverse, engaging with the emerging debate on pluralism in the philosophy of set theory, as well as the mathematical questions to which they lead, such as my work on the modal logic of forcing and set-theoretic geology. I was interviewed by Richard Marshall at 3:AM Magazine about my work (and see other mentions of me in the news). Please edit my Wikipedia entry.
Before that, my permanent position for many years was Professor at The City University of New York, at the Graduate Center of CUNY and the College of Staten Island of CUNY.
I have also held various academic faculty positions at other universities and institutions around the world.