Aquinas's Way to God: The Proof in De Ente et Essentia

"The argument for God’s existence that Gaven Kerr discusses and defends in this book is a very interesting argument in a couple of respects. First of all, this is an argument which doesn’t in an obvious way appear in Aquinas’ list of the Five Ways in the Summa Theologiae . Its status relative to the rest of what Aquinas has to say on the subject of natural theology is a matter of some debate among Thomists, that is to say among followers of Thomas Aquinas. Some would argue – and I have argued this in my book on Aquinas – that the argument of De Ente et Essentia is at least implicit in one of Aquinas’ Five Ways. Other interpreters would argue that it’s entirely different from any argument that he gives in the Five Ways. But many twentieth century Thomists took the view that the argument of the De Ente is actually the core Thomistic argument for God’s existence; this one more than any other argument reflects Aquinas’ understanding of how we reason from the world to God. It gets more closely than any other argument does to the core of God’s nature, for Aquinas. That’s the view that some have taken, in any case. So, what is the argument? The argument is essentially this. In this little book ‘On Being and Essence,’ which Aquinas wrote very early in his career, Aquinas made a distinction between the essence of a thing and its existence. The essence of a thing, you might say, is what a thing is. The existence of a thing is the fact that it is. Suppose that you were explaining the natures of certain creatures to someone – a child, say – who had never heard of them before. So, you explain what a lion is. You give a complete description of the ‘essence’ of a lion – of what it is to be a lion. Then you give a complete description of the essence or nature of a Tyrannosaurus Rex. And then, finally, you give a complete description of the nature or the essence of a unicorn. Then you ask, of these three creatures that I described for you, one of them still exists, one of them used to exist but has gone extinct, and the third never was real in the first place. Based on the description I gave you of the essences of each of these creatures, tell me which is which. And, as Aquinas would note, the child would be unable to do so. Knowing the essence of a lion, a Tyrannosaurus Rex, and a unicorn would not be able to tell you which, if any, of those creatures exist. The existence of a lion is distinct, therefore, from its essence or nature. These are two different principles or aspects of a thing. The argument begins with this distinction between the essence and existence of a thing. This is a distinction that does a lot of work in Aquinas’ work elsewhere, but the way that it plays a role in Aquinas’ argument for God’s existence is as follows. Aquinas thinks that anything in which there’s a distinction between its essence and existence requires a cause for its existence. With a lion, for example, there’s nothing in the essence or nature of a lion that entails its existence. Its existence has to come from something outside of it. It has to be added to it, you might say. It’s not built in. And that is true not only when the lion first comes into being but at every moment at which it exists. Its existence has to be added to it from outside, precisely because it’s distinct from its essence or nature. For a lion to exist here and now, even for an instant, there must be something adding existence to its very essence here and now. There must be something imparting existence to it here and now. But if that thing which is imparting existence to it is in the same metaphysical boat, as it were, if it is itself something whose essence and existence are distinct – so that it too needs existence to be added to its essence or nature — then that thing too will require some cause for its existence here and now. So, we have a regress. The only way we can break this regress, in Aquinas’ view, is if we get to a cause which imparts existence to other things without getting it itself from something else. This is something that has its existence built into it, you might say. This would be something whose very essence just is existence. There’s no difference in it between its essence and nature, on the one hand, and its existence on the other. Rather, its entire essence or nature just is existence. To use fancy jargon, it is what Aquinas calls ‘subsistent being itself’. This, Aquinas says, as he does in the Five Ways, is what we call God. He would then proceed to argue that anything that’s like this – anything that just is subsistent being itself – would have to have the various divine attributes. Here is one of several areas where Aquinas’ account of theological language becomes very important. Aquinas is committed to something which is often called ‘the doctrine of analogy’ by commentators. The idea here is that there are three basic ways in which we use language. We might use language in a univocal way, where we use two different terms in exactly the same sense. If I talk about a baseball player swinging a baseball bat and a cricket player swinging a cricket bat, we’re using the word ‘bat’ in the same sense. There are differences between baseball bats and cricket bats, but they’re essentially the same kind of thing. A second way in which we might use language is equivocally. If I talk about a baseball bat and then talk about a bat that was flying in the attic and inspired Bruce Wayne to become Batman, here I’m using the word ‘bat’ equivocally. In one case I’m using the word ‘bat’ to refer to a stick that’s used in a certain sport, in the other case I’m using the word ‘bat’ to refer to a certain flying animal. But Aquinas holds that there’s a third way in which we can use language, which he called the ‘analogical’ use of language. The analogical use of language is a middle ground between the univocal use and the equivocal use. And it’s not a metaphorical use. To be more precise, metaphor is one kind of analogical use of language but it’s not the only kind. There are analogical uses of language that are literal rather than metaphorical but are still not univocal or equivocal. One example of this would be the term ‘good’. “When we say that God has power or we say that God has goodness, we are not saying that he has exactly what we have but just more of it. But we’re not saying either that what he has is completely unrelated to what we call power or goodness in us.” Think of the way that we might describe a meal as good. You might say that the pizza I had for dinner was a good pizza. Or you might describe the book you are reading as a good book. Or you might describe someone as a good man. Aquinas would say that when we use the term ‘good’ in these three contexts, we’re not using the term in a univocal way. The goodness of food is very different from the goodness of a man. I guess a cannibal might use the terms in the same way, but unless we’re talking about a human being as a kind of meal then we’re not using the word in the same way. The moral goodness of a human being and the nutritional goodness of food or the literary goodness of a book are not exactly the same thing. But we’re not using the word equivocally either. It would be wrong to say that the goodness of a human being or the goodness of a book are entirely unrelated to the goodness of food, in the way that being a baseball bat and being a bat that flies around your attic are completely unrelated. We are using the word in an ‘analogical’ way, for Aquinas. We are saying that there is something in the goodness of a book that is analogous to the goodness of food. And there is something in the goodness of the food that is analogous to the goodness of a human being. It’s not the same thing, but it’s not completely unrelated either. Get the weekly Five Books newsletter For Aquinas, everything we say about God has to be understood in this analogical way. When we say that God has power or we say that God has goodness, we are not saying that he has exactly what we have but just more of it. But we’re not saying either that what he has is completely unrelated to what we call power or goodness in us. What we’re saying, rather, is that there’s something in God that is analogous to what we call power or goodness in us and so forth. So, to come back to this question of God being a cause, the way in which God is a cause of things is not exactly like the way that one thing in the world of our experience might cause another thing. The way things in the world cause each other, for example, is sometimes by way of physical contact, as when one billiard ball hits another. But that can’t be the way that God causes things in the world or causes something to exist here and now, for example, because God is not a physical object and so doesn’t have a physical surface that can make contact with some other physical surface. And in every other way too, God is unlike a physical cause. So, when we describe God as a cause, this would be a classic case for Aquinas of when we’re using a term analogically rather than univocally. We’re saying there’s something in God that is analogous to what we call causation in our experience even though it’s not exactly the same thing. Kerr’s book is important for a couple of reasons. First of all, it’s really the first booklength presentation and defense that I know of of this particular argument of Aquinas. Anyone who wants to study this particular argument of Aquinas in depth has to read Kerr’s book. It’s also a book that’s written, as Brian Davies’ book is, from the point of view of someone who is well-versed in contemporary analytic philosophy and therefore who is familiar with the moves that contemporary academic analytic philosophers would make, and the concerns or questions that they would have. Kerr is very important for anyone who wants to see how Aquinas’ ideas might be brought into conversation with contemporary academic analytic philosophy."