The passage of time is a continuing thing. At 18, you're going to live forever, and you are definitely not at 52, so that is a recurring topic. I still think it's the main stuff.
“I must stress here the point that I appreciate clarity, order, meaning, structure, rationality: they are necessary to whatever provisional stability we have, and they can be the agents of gradual and successful change.”
“I don't think it would be a good idea for scientists to have more political power. Scientists as a group are more inclined to try to derive an ought from an is, than the population at large.”