The historical approach to understanding of scientific fact is what differentiates the scholar in science from the mere experimenter. - Edwin Boring

Leibniz foreshadowed the entire doctrine of the unconscious, but Herbart actually began it. Wundt was to appeal first to unconscious inference in order to explain perception, and then to apperception. Fechner was to take from Herbart the notion of the measurement of the magnitude...

Titchener interest lay in the generalized, normal, adult mind that had also been Wundt's main concern.

It is not likely that the history of psychology can be written in the next three centuries without mention of Freud's name and still claim to be a general history of psychology... Perhaps, had Freud been smothered in his cradle, the times would have produced a substitute, It is hard to say. The dynamics of history lack control experiments.