“War has given applied psychology a tremendous impulse. This will, on the whole, do good, for psychology, which is the largest and last of the sciences, must not try to be too pure.”

Applied psychology had committed itself to knowledge goals that were unlikely to be advanced by the kind of investigative practice associated with Wundt's laboratory. What it was after was knowledge that could be quickly utilized by agencies of social control so as to make their work more efficient and more rationally defensible.
66
Constructing the subject: Historical origins of psychological research. 1994

Evolution and Ethics (1893)
Context: The history of civilization details the steps by which men have succeeded in building up an artificial world within the cosmos. Fragile reed as he may be, man, as Pascal says, is a thinking reed: there lies within him a fund of energy, operating intelligently and so far akin to that which pervades the universe, that it is competent to influence and modify the cosmic process. In virtue of his intelligence the dwarf bends the Titan to his will. In every family, in every polity that has been established, the cosmic process in man has been restrained and otherwise modified by law and custom; in surrounding nature, it has been similarly influenced by the art of the shepherd, the agriculturist, the artisan. As civilization has advanced, so has the extent of this interference increased; until the organized and highly developed sciences and arts of the present day have endowed man with a command over the course of non-human nature greater than that once attributed to the magicians.... a right comprehension of the process of life and of the means of influencing its manifestations is only just dawning upon us. We do not yet see our way beyond generalities; and we are befogged by the obtrusion of false analogies and crude anticipations. But Astronomy, Physics, Chemistry, have all had to pass through similar phases, before they reached the stage at which their influence became an important factor in human affairs. Physiology, Psychology, Ethics, Political Science, must submit to the same ordeal. Yet it seems to me irrational to doubt that, at no distant period, they will work as great a revolution in the sphere of practice.<!--pp.83-84

Cited from Lord Rayleigh, The Life of Sir J. J. Thomson (1943), p. 199.
Attributed

Letter to Carl Jung, (16 June 1948)
Context: The purely psychological interpretation only apprehends half of the matter. The other half is the revealing of the archetypal basis of the terms actually applied in modern physics. What the final method of observation must see in the production of "background physics" through the unconscious of modern man is a directing of objective toward a future description of nature that uniformly comprises physis and psyche, a form of description that at the moment we are experiencing only in a prescientific phase. To achieve such a uniform description of nature, it appears to be essential to have recourse to the archetypal background of the scientific terms and concepts.

Source: The Theosophical Glossary (1892)

Source: Psychology and Industrial Efficiency (1913), p. 18-19

Source: Principles of Gestalt Psychology, 1935, p. 22. ( Chapter 1 https://www.marxists.org/reference/subject/philosophy/works/ge/koffka.htm, online at marxists.org)
Context: Psychology is a very unsatisfactory science. Comparing the vast body of systematised and recognised facts in physics with those in psychology one will doubt the advisability of teaching the latter to anybody who does not intend to become a professional psychologist, one might even doubt the advisability of training professional psychologists. But when one considers the potential contribution which psychology can make to our understanding of the universe, one's attitude may be changed. Science becomes easily divorced from life. The mathematician needs an escape from the thin air of his abstractions, beautiful as they are; the physicist wants to revel in sounds that are soft, mellow, and melodious, that seem to reveal mysteries which are hidden under the curtain of waves and atoms and mathematical equations; and even the biologist likes to enjoy the antics of his dog on Sundays unhampered by his weekday conviction that in reality they - are but chains of machine-like reflexes

Source: Motivation and Personality (1954), p. 234.

Source: Existence (1958), p. 13; also published in The Discovery of Being : Writings in Existential Psychology (1983), Part II : The Cultural Background, Ch. 5 : Kierkegaard, Nietzsche, and Freud, p. 52