Brian Leiter points at a memorial notice for the late John Rawls, one of the leading (probably the leading) American political philosopher of the twentieth century. I got to know Rawls just a little bit, when as a graduate student I sat in on one of his classes. He was both one of the warmest and one of the most intelligent people I have ever had the privilege to meet.
The class I took was offered both to undergraduates and graduate students; there were twice-weekly lectures, plus weekly discussion sections. The sections for undergrads were led by philosophy grad students, while Rawls himself led the session for grad students. I asked whether I could sit in on the grad-student section, given that I was an astronomy grad student who was merely auditing the class; being the paragon of fairness that he was, he said that since I was a grad student, I should go to the section for grad students, simple as that.
Unfortunately, I almost never got to talk with him about philosophy; once he found out that I was interested in cosmology and the early universe, he was always asking me questions about that. He had wide-ranging interests in math and science, and would often use metaphors in the lectures that I’m sure nobody but me could appreciate. The best was when he said that deriving his two principles of justice should be like proving Stokes’ theorem in differential geometry on an arbitrary manifold: it required a large investment to set up the definitions and axioms, but then the proof was almost immediate. He also had a standing offer of $100 to anyone who could find a “mistake” in his theory of justice as fairness, in the sense of an incorrect conclusion drawn from his premises. He believed that good philosophy should be like good mathematics; it need not be “right” (if you didn’t believe in the premises), but it could be free of mistakes.
He influenced my own views a great deal, moving me from a confused utilitarianism to a fervent social-contractarianism. A rare combination of genius and genuine humanity.