Ethymologically, psychology means "the science of the soul." This science is as old as philosophy itself. Every great system of philosophy, from the beginning to the present, has dealt explicitly with this subject, containing a more or less clearly defined presentation of matters relating to it. But if the science is old, the word is comparatively new, tracing back not further than the sixteenth century, when a Marburg professor, Goclenius, used it to title one of his works. The credit, however, for bringing the word into general use would seem to go to another German, Christian Wolff (1679-1754). With his Psychologia Empirica (experimental psychology), published in 1732, and his Psychologia Rationalis (rational psychology), published in 1734, he popularized not only the word "psychology" but also a distinction that was to have a long career. Kant, for example, made use of the same terminology.
During the course of the nineteenth century the word and the distinction became popular in France as well, gaining general acceptance through a development in which the influence of Maine de Biran (1766-1824) and the French Rationalists and Eclectics was decisive. Thus, on the whole and by a strange paradox, the word "psychology" comes into its own at the very moment when, in large measure, those who profess to deal with the subject deny the very possibility of any knowledge of the soul itself. In these circumstances we may ask what meaning this term conveys in the vocabulary of one who intends to direct his philosophical inquiry along the paths followed by St. Thomas. Before answering this question, however, we ought to review the principal historical movements regarding the doctrine of the soul, for the answer is best seen against its historical background.
1. Historical Survey
Throughout antiquity and the Middle Ages there were two main schools of thought regarding the soul. One was the more spiritualist view, taught by Plato and St. Augustine; the other a more empirical view, represented by Aristotle and his followers. In the thirteenth century, as is well known, it was the latter doctrine that came to prevail, as did the rest of the philosophy of the Stagirite. Ever since, Christian philosophy in the main has been Aristotelian.
With the birth of modern thought the psychology of the Schoolmen, together with everything that came from Aristotle, fell into disesteem. But the science of the soul could not lie entombed forever; men felt the need to resurrect it. One of the first to make the attempt was Descartes (1596-1650), who revived the excessively spiritualist view of the Augustinian school, which leaned toward excluding the body in the study of the soul. But Descartes was also something of an innovator in the field by making reflection upon self the basic principle or starting point of all knowledge. From then on, the term quot;psychological" tended more and more to mean "accessible to consciousness." Nevertheless, the substance of Cartesian psychology remained essentially metaphysical in character; its principal object of inquiry was still the soul itself, that is, the essential nature of its being.
In the eighteenth century, owing to the influence of John Locke (1632-1704), a new step was taken, one that aimed at complete elimination of traditional metaphysical considerations from the science of the soul. Psychological facts were now reduced to purely observable phenomena, behind which the soul and its powers lay, it was thought, inaccessible. Psychology sought to become a purely empirical science, comparable to other sciences of nature; its domain was confined to consciousness, that is, to what was obtainable by direct conscious experience.
Following the method of appeal to consciousness and empirical inquiry, psychological research made great strides. Even though metaphysical speculations regarding the spiritual were not wholly neglected - witness, for example, Lachelier (1832-1918) or Bergson (1859-1941) in France - the main concern of psychologists was to establish an independent and scientific psychology from which the higher problems of the soul and its destiny were to be excluded. The remarkable progress that had been made by the experimental sciences seemed to justify even the fondest hopes of like success in psychology. Since it was possible to systematize and interpret the findings of physical science according to strictly scientific methods, why should it not be possible to do likewise with findings of the mind? Away with, or let others wrangle about questions of the soul and its faculties, and, for that matter, about the essence of material things. Keep to the observation of precise facts and to the formulation of carefully controlled laws. In this way, it was thought, you would achieve a psychology that was truly scientific and objective, one that could rally the allegiance of all concerned. Roused by this promise, psychologists everywhere applied themselves intensively to the task of observation and experimentation, a task to which, it must be acknowledged, we are indebted for the imposing results that are the boast of the modem science of the soul. For all practical purposes, moreover, this times.
Still, it may be asked whether the hope of developing such a science is altogether justified; whether in the last analysis it is possible to establish a completely autonomous science of psychology. More precisely, is there any warrant for believing there can be a separate psychology conceived after the manner of the experimental sciences, which would be distinct but companion to the older metaphysical study of the soul, whose truth is perennial? This is the question that must now be answered.
2. Rational Psychology and Experimental Psychology
Before the eighteenth century there was but one branch of systematic psychology, forming a part of an over-all philosophical program and treated according to the methods of philosophy.
What are the characteristics of this psychology? In the first place, the older psychology is definitely philosophical in character, in the sense that it seeks to determine the very first principles of life and its manifestations; in the sense also that it does not hesitate to make use of the more basic notions of Aristotelian philosophy, such as substance and accident, matter and form, act and potency. Secondly, this psychology deserves to be called scientific in the strict sense of the word, endeavoring as it does to explain things by their proper causes. Indeed, this is its main task, and therefore the work of observation and classification is only the preliminary step. Furthermore, despite its admittedly rational or theoretical bent, in its own way the older psychology is also empirical, not to say experimental. Aristotle, in particular, always begins with some well-defined datum of experience. As a matter of fact, the sort of sober empiricism in which the business of interpretation is but a continuation and judicious ordering of experience, strikes us as being the distinctive feature of Aristotelianism. According to this philosophy, then, there is but one science of the soul, which is both empirical and rational. Are we to conclude, therefore, that the principles of this philosophy do not permit us to organize the science of psychology into two separate divisions, commonly called rational and empirical, or to treat one independently of the other? The answer to this question would seem to be no. At the present time, at any rate, such a division is more or less taken for granted. Nevertheless, one or two observations are in order.
For one thing, it should be clearly understood that the distinction of experimental and rational is only relative, thus indicating no more than the line of emphasis followed by one method as compared with the other. Consequently, the terminology of "rational" and "experimental" is, to say the least, unsatisfactory, for it opens the door wide to confusion. The fact is that no science of any kind is possible without both reason and experience. A much better course would be to distinguish these two disciplines in terms of the level of interpretation in which each is engaged. On the one hand we should have a philosophical or metaphysical psychology, which seeks to determine the highest principles of the science; on the other hand, a scientific psychology, scientific in the modern sense, which occupies itself with a more immediate level of interpretation. Furthermore, a so-called experimental psychology could in no way claim the role of ultimate arbiter in regard to the basic problems of the soul; it could not, in other words, pose as an authentic philosophical wisdom. Such a role rightfully belongs to a higher discipline.