It may turn out in the long run that my book Verbal Behavior is more important than the experimental work. I started working on it when I was in the Society of Fellows at Harvard. I had an argument with Alfred North Whitehead, the great philosopher. He said, “Well your behaviorism works except with verbal behavior. How can you explain my sitting here saying something like, ‘No black scorpion is falling upon this table’?” The next morning I got up and started to write Verbal Behavior. That was about 1934 and it was published in 1957, so it took me a good quarter of a century.