Story of Psychology - Morton Hunt [34]
Perhaps worn out by his exertions, Aquinas felt something strange come over him while saying Mass one morning in December 1273; afterward he could not continue his work on the Summa. “I can do no more,” he said. “Such things have been revealed to me that all I have written seems as straw, and I now await the end of my life.” He died three months later, and in less than fifty years was canonized by Pope John XXII.
Aquinas’s theology and metaphysics do not concern us here except as he made psychology harmonize with them. This he did chiefly in three parts of the Summa Theologica: “Treatise on Man,” “Treatise on Human Acts,” and “Treatise on Habits.” Little of what he set forth in these sections was new; he was not an explorer but a reconciler of Christian doctrine and Aristotelianism.
His psychology is based largely on Aristotle (though couched in Aquinas’s own difficult and abstruse terminology), plus odds and ends of Galen, Augustine, and a few others. He restored to psychology much that was sensible and realistic, and had been lost in the earlier patristic writings. But he froze the science in its classically speculative and argumentative mode and built into it certain key items of Christian faith, such as the dualism of body and soul or mind, that would cloud psychology to our own day.
In the psychological sections of the Summa Theologica one can see, despite the fog of Thomist verbiage, many familiar topics.
On perception, Aquinas discusses the five external senses familiar to earlier writers, plus the “common” sense—Aristotle’s notion—by which we recognize that data simultaneously perceived through different senses come from one object.
He subdivides the functions of the psyche, in more or less Aristotelian fashion, into the “vegetative” (its autonomic physical functions), the “sentient” (perception, appetite, locomotion), and the “rational” (memory, imagination, and reason or intellect). But he enlarges significantly a passing suggestion of “the Philosopher” (as he often calls Aristotle) that there are two kinds of intellect. The functions of the first, or “possible intellect,” are understanding, judgment, and reasoning concerning our perceptions; the functions of the second, or “agent intellect,” are to abstract ideas or concepts from our perceptions and to know, through faith, those other truths, such as the mystery of the Trinity, that cannot be known through reason.
Aquinas offers no empirical evidence that two distinct intellects exist; his conclusions are based on a combination of logic and doctrine. For whatever in the soul concerns bodily perceptions, sensations, and emotions—whatever is part of the soul-body unit during life—cannot live on after death. But the soul does live on; doctrine says so. It must therefore be that part of the soul-body unit partakes of higher and eternal knowledge and therefore is immortal; this is the agent intellect.38
Aquinas thus reconciles Aristotelian psychology, which did not allow a personal afterlife, with Christian doctrine, which insisted on it. Yet in making the perishable “possible intellect” the mechanism through which we create ideas, he excludes from his own psychology the mystical Platonic doctrine of innate ideas. He takes his stand with Aristotle that the mind of the infant is a tabula rasa with the power to extract ideas from experience. The doctrine of innate ideas will plague psychology in later centuries, but not through Aquinas’s doing.
He does, however, differentiate between desires rising from the concupiscible appetite and those from the irascible appetite, a dichotomy he took from Galen, who got it from Plato. Aquinas develops it in more detail than his predecessors, organizing the material by means of definition, deduction, and common sense. His schema: When the concupiscible appetite is aroused by a good thing, we feel such emotions as love, desire, and joy; when repelled by an evil thing, hatred, aversion, and sorrow. When the irascible