Philosophy, religious faith, and theology are complementary aspects of the writings and thought of St. Thomas Aquinas, among other religious philosophers. Philosophy is a mode of thought, a means of speculating based on logic and experience. Philosophy is the means by which human beings have of examining their place in the universe. Religious faith is an accepted truth based on belief rather than close analysis. Theology is the study of God and the study of religious teaching. Aquinas combines all three of these conceptions as he analyzes human nature, the relationship between the human being and God, and the meaning of teachings of the Church.
Plato held that the body and the soul were separate and of a very different constitution, while Aristotle saw the soul as form of the body, a view accepted by St. Thomas Aquinas. Thomas was a Christian thinker and accepted the immortality of the soul, but he had to answer the question of whether this made sense given that the closeness of the union of body and soul might mean that the possible subsistence of the soul apart from the body could be ruled out. For Thomas, the soul informed the body but was not exhausted by the process. The soul, he argues, must be a spiritual and subsistent form because it is capable of knowing the nature of all bodies. It cannot be itself the body or it could not reflect on itself. The human soul, says Thomas, must be immaterial, incorruptible, and naturally immortal. Another argument offered by Thomas Aquinas is that there is in the human being a natural desire for immortality, and he says that such a natural desire, implanted by God, cannot be in vain. Man is also the only animal that can conceive of a perpetual existence divorced from the present moment, and this corresponds to the natural desire for immortality (Copleston 383-385).
Thomas Aquinas wrote the Summa Theologica between 1265 and 1273. The third article of the Summa attempts to de...