John von Neumann Quote

Source/Notes: Reply to Dr. Felix Smith at Stanford who had said "I am afraid I don't understand the method of characteristics." As quoted in: The Dancing Wu Li Masters (1979) by Gary Zukav.
Source/Notes: Advice given by von Neumann to Richard Feynman as quoted in Los Alamos from Below in Surely You're Joking, Mr. Feynman! (1985)
Source/Notes: Statement at the start of a classroom lecture, as quoted in 1,911 Best Things Anyone Ever Said (1988) by Robert Byrne
Source/Notes: Attributed to von Neumann by Enrico Fermi, as quoted by Freeman Dyson in A meeting with Enrico Fermi in Nature 427 (22 January 2004) p. 297