"The only way to tell whether a given event is reinforcing to a given organism under given conditions is to make a direct test."

"We shouldn't think about what people feel, but about what they do."

"We shouldn't teach great books; we should teach a love of reading."

"We cannot prove that a man is free, but we can prove that he is not."

"I deny that I have ever attacked anyone's dignity. I have attacked the concept of dignity as a causal agent."