Article 1: “Whether the existence of God is self-evident?”
Here in the first article Thomas rejects the position of St. Anselm according to whom God’s existence is self-evidently known from the mere meaning of the name of God as “that which nothing greater can be thought.” Thomas argues, on the contrary, that because we don’t and can’t know in this life the essence of God, we can’t know intuitively or self-evidentially that his existence is entailed in his essence. Now, as we will see, Thomas does believe that God’s existence is entailed in his essence (indeed, his existence turns out to be nothing other than his essence). The point Thomas is making here, however, is that this fact is not self-evidently true for us, even if it is self-evidently true in itself. This is very important: we must not confuse the order in the way things really are with the order in the way in which we happen to know or experience them, or the order of being with the order of knowledge. Sometimes the order is the same, but not necessarily.
So, as human beings, we don’t ever have the opportunity or ability, at least in this life, to simply look at God and not only say, “well, there he is!” but more than this, to even say, “ah, if that is what God is, then of course he must exist.” Given our creaturely limitations, therefore, the way, that is, God made us to know as humans, to know that God exists, it needs to be demonstrated from those things which we can look at, namely his created effects. Thus, if you look carefully at each of Thomas’s famous “five ways” for proving God’s existence, you’ll notice that they each begin on a characteristic theme. In his argument from motion, Thomas begins by saying that “it is certain, and evident to our senses, that in this world some things are in motion.” Or his argument from efficient causality, which begins this way: “In the world of sense we find there is an order of efficient causes…” Or his third way from the nature of possible being: “We find in nature things that are possible to be and not to be…” Or Thomas’s fourth way, which “is taken from the gradation to be found in things.” Each of the five ways, and any other argument that would aspire to be a true argument for God’s existence (for Thomas, there are other arguments, these are just his faves), must begin in the sensible realm of nature, with things that we can see, touch, taste, smell, or hear. As Thomas further explains, this is not a limitation on God’s part, but rather a limitation on our part, on how God himself has chosen to make us. If we were angels, who are able to know things in an intuitive or non-discursive way, we might not have this problem. (Anselm’s ontological argument: the apologetic of the angels!) What we need, therefore, are arguments that will condescend to and meet our minds where they are at.
This latter point is worth dwelling on briefly here, for it has often been objected by some from within the Reformed apologetic school of thought known as Presuppositionalism that Thomas’s insistence that God’s existence needs to be demonstrated effectively enshrines things like reason, nature, causality, the rules of inference and evidence, and the like, with an autonomous and therefore idolatrous authority which even God is then required to bow down and submit to (if God is to exist, these are the “offices” with which he must register his existence). As Thomas himself might see the matter, however, it is precisely his “presupposition,” if you will, of how God has in fact made the world and the way in which man has been made to know the world, that moves St. Thomas to argue for God’s existence in the way that he does. For St. Thomas, we must begin our arguments for God’s existence with those things that are nearer and clearer to us (though there is an important sense for St. Thomas in which things only ever become “near and clear” to us in light of their relationship to God), and from them work our way to the kind of cause that must exist to produce such glorious effects, because this is the way that God himself has made us to reason about him. To deny the validity of this apologetic method, therefore, is in fact to deny, after a fashion, the very God who authorized it; it is certainly to deny the unique way in which St. Thomas believes God to have made us to know, and exchange it for a way in which he has not made us to know. (It is for this reason, incidentally, that Thomists in the twentieth-century accused the father of modern philosophy, René Descartes, in his resurrection of Anselm’s ontological argument, of being guilty of the sin of “angelism,” of substituting, that is, a properly human psychology and epistemology which depends on the senses and the physical world for the mediation of all its knowledge, for an angelic, if not in fact a divine psychology and epistemology, which does not.)
Now, it is true that traditionalist approaches to St. Thomas have attributed to him a natural theology still very much conceived along the rationalist, foundationalist lines of secular philosophy. However, if Thomas does not exactly take for granted God’s existence at the beginning of the Summa in a fideistic fashion, neither should it be said that he tries to prove God’s existence from some kind of neutral, external standpoint of “pure reason.” For Aquinas, it should be clear, there is and of course can be no external, theologically-neutral standpoint from which the question of God’s existence can be measured or compared to reality itself. How could there be? He is arguing for God’s existence as a Christian, and thus as someone who sees the world as a Christian sees it, and is attempting to elucidate from that vantage point the intelligibility of theistic belief. Thomas is not trying to lay the foundation for a rational, natural theology “from the outside,” one upon which he might then later build his edifice of revealed theology. As was mentioned above (in the short essay on faith and reason in St. Thomas), it is best to see him as approaching the Christian faith as a coherent, integrated worldview comprised of both a natural and a revealed theology, of both a way of faith and a way of reason, which are to be taken together and whose coherence or intelligibility must be appreciated not from some supposed outside, “objective” perspective, but from the inside. In this way, the natural theology of Thomas’s Summa, while not written specifically for the unbeliever, nevertheless has an important application for him. It makes a rational claim upon the non-believer, in other words, without on that account making a concession to the purported autonomy of his rationality.
 My remarks here are influenced by an essay by Aquinas scholar Rudi te Velde, “Understanding the Scientia of Faith: Reason and Faith in Aquinas’s Summa Theologiae.” Chap. 3 in Fergus Kerr, ed., Contemplating Aquinas: On the Varieties of Interpretation (Notre Dame, IN: University of Notre Dame Press, 2003), 55-74.