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Saint Thomas Aquinas

Philosophy & Faith with Father Francis Selman      
More on St Aquinas (including Pope Benedict XVI's catecheses) here

Although St Thomas Aquinas, who lived from 1225 – 1274, was primarily a theologian, he was also a philosopher in his own right, and indeed one of the greatest philosophers. He took his philosophy mainly from Aristotle, but also adapted it to make it compatible with the Christian faith in some matters. As we find the philosophy of Aquinas mixed in with his theology, apart from his commentaries on the works of Aristotle, we need to have in view the overall plan of Aquinas. This was the scheme of exitus and reditus, of all things coming from God and returning to him. They come from God as their Creator, the beginning of all things: they return to him as their end. Although in the opinion of some, Aquinas’ main contribution to philosophy was his philosophy of mind, the most important point of his philosophy, to my mind, is what he says about existence.

If I were to single out one article among all the articles and questions which Aquinas wrote as the key to everything else that he says, it would be this: “If therefore he (God) is not his existence, he will be a being by participation and not by essence. Therefore he will not be the first being, which is absurd to say” (ST 1a 3, 4). With these words, St Thomas draws the distinction between God and all other beings, he is existence itself, all other things are not their own existence because they receive it from another. Their existence is caused, God is uncaused, the uncaused Cause of all other things. Everything that beings to exist receives its existence from something already existent: therefore it shares or participates in existence. St Thomas argued that everything which receives its existence must take us back to some being which does not receive its existence and, therefore, is its existence. This is God. But St Thomas did not draw this distinction between the Creator and all creatures in such a way as to cut off God from the world, as the Neoplatonist Platinus in the 3rd century AD did, who said that the One is beyond all being.

What follows from this? First, as God does not receive his existence from anything already existent, his existence is unlimited: he is infinite. As God’s existence is unlimited, he is all powerful. As he is all powerful, all things come under his power and so under his providence, by which he guides all things. None of the gods of the ancients were thought to be all-powerful, simply because there were many of them, but Aquinas could show by reason that there is one source of all existence. Aristotle’s God was the unmoved Mover who is the source of all motion in the universe but not the source of all existence, because his unmoved Mover did not produce the matter of the universe: Aristotle had to suppose it was just there, because none of the ancient Greeks could grasp the idea of creation, to make something out of nothing, as they all said “nothing comes from nothing”.

St Thomas was thus also able to show that the heresy of the Manichees was not just against Scripture and the Christian faith but also contrary to reason. The Manichees taught that the material universe is not the product of God but of some rival being, a demon, who is the principle of evil and darkness as opposed to goodness and light. But Aquinas shows that there can only be one source of all existence as there can only be one Being who is Existence itself. Thus the Creator of spirit and soul is none other than the Maker of all material things. There is only one Creator of all things, immaterial and material. Moreover, everything, including matter, is good in itself. But we know that nothing made is its own good because it shares in goodness as it shares in existence: there is always some good beyond it, which is a higher good. As no creature is its own good, it is not its own end. Thus God, beyond whom there is no greater good, is the end of all things. Aquinas remarks that all things, in seeking their good, even unknowingly, seek God (ST 1a 44, 4 and 3). God is the beginning of all things as the source of all existence, and the end of all things as the Good itself.

Aquinas thought that there is a scale of being in the universe. God did not just make material things but immaterial ones: these are angels and souls. Some of these, angels, are purely immaterial like himself. Others are joined to material bodies: these are human souls. Unlike Plato, who thought that the soul was better separated from the body, Aquinas maintained that it was natural for the soul to be united to the body. Like Aristotle, he held that the soul is united to the body as its form, because it makes the body a living thing. For Aquinas, a human being is a unity of body and soul. Only on this understanding of a human person can we see the point of resurrection if it is better for the soul to be without the body. In Plato’s view, sense-perception only reminds us of the Ideas which the soul knew before it entered the body, but in Aristotle and Aquinas sense-perception plays a key role in our knowledge, because the body’s senses are involved as we are a unity of body and soul. As Aquinas said, “Our knowledge takes its beginning from the senses.”

Aquinas’ theory of how we acquire our ideas (his philosophy of mind) is very like Aristotle’s. Once Aristotle had argued against the existence of Plato’s Ideas, the soul could not know them by clearly seeing them in a previous existence; so there had to be some other way we get our ideas and general concepts. Aristotle said that we abstract them from sense-impressions. For example, I have sense-impressions of particular horses, from which I conceive my idea of what a horse is. This idea is general, not of any particular horse with a particular colour as a horse exists in matter. As a general idea of a horse is not as a horse exists in its material conditions with its particular features, the idea is immaterial. Of course the mind could not have general ideas like this if it were material. If it can think of things in an immaterial way, it is immaterial, and the soul of which it is a power must be immaterial. If the mind were material we could only know things as the senses do, which is particular horses in this field, not have the general idea of a horse that fits all horse. Thus Aquinas said that human beings exist on the border (in confinio) between the material and immaterial. Thus we are a kind of microcosm of the whole world as we alone combine the material and immaterial. We are made to get our knowledge through the senses of the body but we can also think of things not just as they exist in matter, which is as particular or individual things, but also generally (Quastiones de anima 1).

It is not clear what Aristotle thought about the immortality of the soul. This presented a difficulty for him, since it seems that if the soul is the form of the body, it cannot exist on its own separately but must perish with the body. Aquinas, however, showed that, as the mind is immaterial, it has an activity, thinking, which is not a power of the body and so the soul can exist on its own because in some way independent of the body.

In Aquinas’ view we reach our end by our actions. We only reach our proper end when our actions are directed to our end. These are virtuous actions in accord with right reason. But our end is not so much happiness but beatitude. We can only reach this by actions helped by grace, which we receive through Jesus Christ who, as he is God and man, is our way of returning to God, our end."