Cumulative Record. Chapter 23: Current Trends in Experimental Psychology. Quote 8

It is not true that human behavior is not controlled. At least we cannot proceed very far as scientists on that assumption. To have a science of psychology at all, we must adopt the fundamental postulate that human behavior is a lawful datum, that it is undisturbed by the capricious acts of any free agent—in other words, that it is completely determined. (pp. 345)