What are the sources to be used in constructing a Thomistic psychology? First and foremost, obviously, are the works of Aristotle himself, for these supply not only the foundation but most of the superstructure as well.
1. The Biopsychological Accomplishment of Aristotle
a) The biopsychological writings of Aristotle. - This portion of the Aristotelian corpus includes a whole series of important works. As listed below, they are divided into three principal parts, a division that is generally accepted:
i. The De Anima (in 3 books)
ii. The Parva Naturalia, a collection of the following smaller writings:
De Sensu et Sensato
De Memoria et Reminiscentia
De Somno et Vigilia and De Somniis
De Divinatione per Somnum
De Longitudine et Brevitate Vitae
De Vita et Morte
De Respiration
iii. A group of books dealing specifically with natural science in the ancient sense of animal study:
Historia Animalium
De Partibus Animalium
De Motu Animalium
De Incessu Animalium
De Generatione Animalium
Besides the aforesaid, a work called De Plantis has been attributed to Aristotle, but it is hardly genuine. By contrast, all the other works mentioned appear to be authentic.
b) The place of psychology in the philosophy of Aristotle. -
There is no doubt that Aristotle regarded the study of living beings and their principle, the soul, as a part of the philosophy of nature. But it is also true that at the end of his inquiry into the soul he has found an activity that is independent of the body. This activity, which is thought, opens new avenues of speculation and even prompts him to raise anew, but without deciding it, the very question as to whether this science belongs to natural philosophy. Be that as it may, his biopsychological writings, such as we have them, savor strongly of what has come to be known as natural and biological science. As for the place where psychology belongs within the philosophy of nature as a whole, we can say that the plan followed by Aristotle in natural philosophy is to go from the more universal to the more particular. Thus, he begins by considering motion and mobile being in general. Then he studies each kind in particular, with special emphasis on that movement we call life, and that mobile being which is the principle or source of vital movement, the living being. As set forth by the Stagirite, then, the subject of psychology is a particular kind of body among other bodies, and the science corresponding to this subject is but a particular section of the general study of nature.
c) The formation and development of the psychology of Aristotle. - A point of discussion among students of Aristotle is whether his psychological, or more correctly perhaps, his biopsychological works were all written at a time when his thought had, so to speak, crystallized; or whether they are so many distinct contributions, representing different stages of development? Speaking for Aristotle's philosophy as a whole, the German scholar, W. Jaeger, believes it reveals a pattern of development, ranging from a sharply defined metaphysical and Platonic character in the beginning, to a more empirical form in the end, when Aristotle had disembarrassed himself of the theory of ideas.1 Granting such a gradual unfolding of Aristotle's thought in general, would it be true of his psychology in particular? This question is the subject of a more recent work by F. Nuyens, who traces what he considers to be such a progressive development.2
In his earlier writings, according to Nuyens, Aristotle adhered to the Platonic view of the soul, considering it in sharp contrast, not to say opposition, to the body. The next period was one of transition, producing writings of lesser importance in which soul and body are brought closer together. The third and final period is represented by his great works, in which at last Aristotle had found his own cardinal doctrine, declaring the soul the form of the body. This doctrine, moreover, was to give course and direction to his whole psychology. If this diagnosis is correct, the central point around which Aristotle's own psychology gradually assumed definite and original form, was the matter of the soul's relation to the body. This problem, moreover, was still not completely disposed of in the final stage of development, for at the end of his inquiry Aristotle faces a dilemma. On the one hand the soul as psyche and substantial form, was joined to the body; but at the same time, as nous or principle of spiritual operations, it also transcended the body. On the whole, however, Aristotle's thought would appear to have undergone progressive development in the direction of everincreasing embodiment of the soul.
On the basis of the foregoing remarks we shall assume, for our present purpose, that the principal psychological writings of the Stagirite, the De Anima in particular, stem from the period when, by general consensus, the growth of his thought had already reached its final and lasting stage. Consequently, we may regard them as a uniform source of information.
d) The order of the biopsychological treatises of Aristotle. -
A further question is whether in writing his various psychological works Aristotle followed a certain order or over-all plan. If so, what was it?
Following St. Albert, St. Thomas puts the general study of the soul, the De Anima, at the beginning. This work, he believes, is to furnish the directive principles for the study of the other treatises, since in all living things the principle of activity is a soul. Following the De Anima would be the other works, dealing with different kinds of living beings and their parts and functions. Even though this sequence is not without logical ground, some of the other great commentators, such as Alexander of Aphrodisias and Averroes, take a different view.5 According to them the writings treating of the physical parts of animals should come first; next, the De Anima, which studies the substantial form of living beings; lastly, the other works, in which inquiry is made into the more particular characteristics and functions of living beings. This arrangement, which would seem to merit preference, has the advantage of giving bolder relief to the physical or bodily considerations that are so prominent in this psychology. In other words, the latter course not only avoids the extremely spiritualist or metaphysical procedure that stillhad its followers not so many generations back, but it is also more in harmony with present-day methods of psychology, in which the study of the organism plays a paramount role. Seen in this light, Aristotle's psychology appears very modern indeed.
2. The Psychology of St. Thomas
a) The psychological writings of St. Thomas. - With reference to psychology St. Thomas, as previously noted, may be considered either as a commentator of Aristotle or as a theologian making use of and rounding out a psychological doctrine in furtherance of theological problems. As for the commentaries, those on the De Anima, on De Sensu et Sensato, and De Menloria et Reminiscentia are authentic; the others usually found in the complete editions of St. Thomas' works are apocryphal.4 Among his theological writings there are three principal works in which psychological questions are treated at length and in order: Summa Contra Gentiles, Bk. II, chaps. 56-101; Summa Theologiae, Ia, qq. 75-89; and the Quaestio Disputata de Anima. In addition, there are countless smaller passages scattered throughout his works, especially in the Quaestiones Disputatae de Veritate, De Potentia, and De Malo.
b) The sources. - The sources for St. Thomas' psychological doctrine vary with any given question and must be ascertained in each particular case. The basic source, of course, is Aristotle, on whose principal writings not only in psychology but also in other fields St. Thomas, having long searched and made them his own, wrote commentaries rich in detail and sure of insight. But he also makes frequent use of the great commentaries of antiquity (those of Alexander of Aphrodisias, Simplicius, Philoponus, Themistius), together with those of the Jewish and Arabian commentators of medieval times. Nor should it be overlooked that the psychology of St. Thomas also owes much to various writings of Platonic inspiration, even if sometimes by way of mere reaction to them. St. Augustine, for example, must be regarded as one of his most constant teachers, seeing that his great genius had already raised and thoroughly sifted the problems of the soul as seen in the light of the Christian message.
c) Modern commentaries and studies. - As was to be expected, the great commentaries and writings of later Scholastics in regard to problems of the soul were inevitably based on the work of St. Thomas. Particularly noteworthy as most true to St. Thomas' doctrine are those of Cajetan, Sylvester of Ferrara, and John of St. Thomas, the latter being the only one who treated the whole subject in systematic fashion.5 The manuals of many present-day Scholastics merely reproduce the work of John of St. Thomas.
As for modern interpreters of Aristotle, especially worth mentioning in the present instance are Rodier, who has made a French translation and commentary of the De Anima; the English Aristotelian Scholar, W. D. Ross, under whose editorship the works of Aristotle have been translated into English, and who himself has written a study of Aristotle's philosophy as well as commentaries on the Metaphysics and the Physics; and F. Nuyens, whose more recent inquiry into the development of Aristotle's psychology has already been mentioned.6