“You must bring out of each word its practical cash-value, set it at work within the stream of your experience. It appears less a solution, then, than as a program for more work and more particularly as an indication of the ways in which existing realities may be changed. Theories thus become instruments, not answers to enigmas, in which we can rest. We don't lie back upon them, we move forward, and, on occasion, make nature over again by their aid.”