The Logic of Psychology

The recent presidential address to the American Psychological Association by Dr. Lee J. Cronbach⁹ on the Two Disciplines of Scientific Psychology, may some day come to be seen as a momentous turning point in the history of our science. The two disciplines are experimental and correlational (or observational) psychology; both of these, Cronbach states, are essential branches of psychology, and both must be given due weight in a unified science.*

Objections to such a point of view have come historically from the experimentalists who (cf. Hull¹⁹) have held that theirs alone is the approach which deserves the name of true science; observational methods are at best ad hoc adjuncts to real science. This experimentalist-behaviorist attitude is the one that has generally prevailed in American psychology for the past three or four decades. If Cronbach's thesis is accepted, as it should be in time, much of what has been written and taught about scientific method in psychology is incorrect, and has led to a large amount of waste motion on the