For many things we can find substitutes, but there is not now, nor will there ever be, a substitute for creative thought.

In Chemical and Engineering News, November 10, 1952, as quoted by Alan Tower Waterman in Research for National Defense, in the Bulletin of the Atomic Scientists (March 1953), Vol. 9, No. 2,ISSN 0096-3402, published by Educational Foundation for Nuclear Science, Inc., p. 39.