The physicist Richard Feynman turned out some fantastic and inspiring popular writing. (Surely You're Joking, Mr. Feynman is a personal favorite.) But there's nothing like watching and listening to the great scientist as he thinks out loud.
YouTube has a great collection of Feynman clips, including this one on uncertainty. An excerpt: "I have approximate answers and possible beliefs and different degrees of certainty about different things, but I'm not absolutely sure of anything and there are many things I don't know anything about, such as whether it means anything to ask why we're here . . . I don't have to know an answer. I don't feel frightened by not knowing things, by being lost in the mysterious universe without having any purpose, which is the way it really is, as far as I can tell, possibly. It doesn't frighten me."
That's one of the most original minds of the 20th century talking.—Gregory Mone