P. A. M. Dirac, “Development of the physicist’s conception of nature,” in The Physicist’s Conception of Nature, ed. by J. Mehra. D. Reidel Publishing Co., Dordrecht, Holland, 1973, p. 1.
I found this speech in a collection of lectures from a symposium held in honor of Dirac’s 70th birthday in 1971. This was the opening lecture given by Dirac himself, so you can imagine this old bumbling physicist walking slowly onto the stage, about 35 years after winning his Nobel Prize, and speaking to an audience of friends and peers and equally well-known scientists.
I am in the process of transcribing it. Here is a link to the “live” document: http://bit.ly/cNXxMH
As of May 3rd, 2010, I have typed about four pages. I’ll try to remember to post a comment when I’ve made some significant progress, so if subscribing to the comments feed is one way to know when to check back in.