Théodule Ribot, answered from the texts and cited to the page.
For too long the study of mind was the handmaid of metaphysics, deducing the faculties of the soul from first principles in the philosopher's armchair. I hold that psychology must break with this and become a positive science, taking its place among the natural sciences — observing mental phenomena as it finds them, connecting them to the conditions of the organism, borrowing the method of the physiologist and the evidence of the clinic and the laboratory, renouncing every question it cannot answer by observation.1
It is a psychology without a soul — not because I deny that men have inner lives, but because the substantial soul is a metaphysical hypothesis the science does not need and cannot use. Let the philosophers keep the question of the soul's nature and destiny; the psychologist studies memory, attention, emotion, will, and their disorders as functions, as the physiologist studies digestion and respiration. Only by this renunciation does psychology become a science at all.234
If his work is a science, it must be confessed that it resembles nothing else that bears that name. The new psychology differs from the old in its spirit: it is not metaphysical; in its end: it studies only phenomena; in its procedure: it borrows as much as possible from the biological sciences.German Psychology of To-day, pp. 5–7
That is, in two words, what we find in thousands of books, memoirs, observations, or experi ences; an immense mass of facts which still awaits its Kepler or its Newton. Let us now bring these experimental data into con nexion with the little which antiquity has left us on this subject (Aristotle: Treatise on the Soul, Sensation, Memory, Sleep, etc.).English Psychology, p. 23
And yet this is not in reality surprising; there are very plain reasons for it: in the first place, because the genius which was expended in solving the insoluble and finding the undiscoverable is now devoted only to purely scientific researches; and in the second, because the aim of science is changed; theories are now subordinated to facts, and not facts to theories; systems pass away, but experiences remain.English Psychology, pp. 9–10
In proportion as the old habits of mind are effaced, will we see, more and more clearly, that psychology and metaphysics, formerly confounded under the same title, presuppose intellectual aptitudes that are opposite and exclusive.German Psychology of To-day, pp. 3–4
Ribot's programmatic separation of psychology from metaphysics is the founding move of the discipline in France and parallels Wundt's and James's establishment of psychology as an empirical science elsewhere; it is largely victorious as institutional and methodological history. Its radical descendants — behaviorism's banishment of consciousness, and later the cognitive and neural sciences of mind — carried the "without a soul" program much further. The standing philosophical objection is the perennial one: that a psychology methodologically bracketing the soul, the self, and consciousness may describe functions while leaving untouched the very inwardness that made mind interesting — the hard problem in its nineteenth-century form. Ribot's methodological bracketing (study the functions, leave metaphysics to philosophy) is the standard modern posture, but whether it is a solution or a postponement of the problem of consciousness remains contested.