Quoted in J E Littlewood, A Mathematician's Miscellany, 1953. Everything should be made as simple as possible, but not simpler. I don't believe in mathematics. Quoted in Carl Seelig.
Imagination is more important than knowledge.
The most beautiful thing we can experience is the mysterious. It is the source of all true art and science. What I Believe. The bitter and the sweet come from the outside, the hard from within, from one's own efforts. Out of My Later Years.