Argument 4: I Imperfectly Understand this Argument—Therefore GodWe come now to St. Thomas Aquinas' Fourth Way, the argument from goodness, or perfection, or degrees—however you want to sum it up! Here is the argument in St. Thomas' own words:
The fourth way is taken from the gradation to be found in things. Among beings there are some more and some less good, true, noble and the like. But "more" and "less" are predicated of different things, according as they resemble in their different ways something which is the maximum, as a thing is said to be hotter according as it more nearly resembles that which is hottest; so that there is something which is truest, something best, something noblest and, consequently, something which is uttermost being; for those things that are greatest in truth are greatest in being, as it is written in Metaph. ii. Now the maximum in any genus is the cause of all in that genus; as fire, which is the maximum heat, is the cause of all hot things. Therefore there must also be something which is to all beings the cause of their being, goodness, and every other perfection; and this we call God. (Summa Theologica, I.2.3.Resp.)I'll admit from the get-go that this argument is the one that I understand the least, and is the one that seems to be least understood by most people. Some think it's a variation on the ontological argument, but St. Thomas rejects the validity of the ontological argument because it is an a priori argument, essentially arguing for God's self-evidence. St. Thomas rejects the idea that God is self-evident and that we can have any a priori knowledge of God. His Five Ways are specifically a posteriori arguments for precisely this reason. People who criticise the fourth way as a species of the ontological argument, then, have simply misunderstood it. Others try to refute or dismiss it because they think that it is based on a notion of Plato's "forms", or because St. Thomas' example of fire being the maximum form of heat is bad science—in other words, it's based on a bad cosmology and therefore irrelevant. In fact, Thomas' limited Mediaeval understanding of the natural sciences is irrelevant to the argument, as are Plato's forms (which St. Thomas didn't even believe in). A final criticism is foisted by those who wish to claim that perfection is a subjective term that exists only in the eyes of the beholder. I wish I could simply dismiss this critique as patently false, but unfortunately it has the current fashion of the world behind it, and thus actually needs a reply. Of course, even the most postmodern of math professors will still mark you wrong if he asks you, if you have five apples, and you eat two of them, how many do you have left, and you answer with, "My perception of the quantity of remaining apples may be different than yours, and we cannot determine it with certainty, because everything is subjective." I believe, after grappling with this argument, that its difficulty lies in the fact that it requires a bit of lateral thinking to really grasp, rather than the more direct, linear arguments of the first, second, third, and fifth ways.
Like the first three arguments, the fourth argues from the real world back to God, but unlike the first three, which deal with realities experienced by the senses, the fourth deals with realities as experienced by our intellect (which is why it is so often conflated with the ontological arguments for God). There are real things in this world that are not objects, that are not physical, but they are just as real: things like love, justice, truth, beauty, life, etc. It is with regard to these things that the fourth way is formulated.
That is, there are certain qualities of perfection that things possess. These qualities can be divided into "limited perfections" and "unlimited perfections". For example, all animals possess the quality of "animality"—that characteristic that makes all animals, animals, be they ants or dogs or elephants or humans. All animals possess "animality" in its fullness, and nothing that is not an animal possesses animality. This is why it's called a "limited" perfection. It is limited to those things which possess it. Moreover, one cannot possess it in part. Something either is an animal or it isn't. Something is either a plant or it isn't. The particular quality is intrinsic to the thing that possesses it.
On the other hand, there are qualities that are unlimited—that is, they are shared across the different types of things in varying ways. These qualities include goodness, truth, beauty, existence, life, etc. While they are possessed by different types of things, they are not possessed in the same way by all things. In other words, a tree, a car, a bird, and a man can all be "good", but a tree is not good in the same way that a bird or a car is. As well, they are not possessed to the same degree by all things, or even by things of the same kind. One man can be healthy and robust, while another frail and sickly. These men possess the unlimited perfection of Life to varying degrees. Moreover, over the course of his life, a man may grow more and more in goodness, or wane in the same.
Now, if something can be possessed in varying degrees, and if things of different kinds can possess these qualities, it shows that qualities such as life, goodness, and truth are not intrinsic to the thing itself. A man possesses his humanity intrinsically, but he possesses goodness extrinsically—in other words, the unlimited quality does not belong to him, but he has received it from somewhere.
The recognition of degrees of unlimited perfections points to the fullness of that perfection somewhere. We realise that insofar as something has a limited degree of a particular perfection, there is a corresponding degree of potential perfection. As such, there must be a fullness of that perfection, otherwise it isn't a perfection. These unlimited perfections must be possessed in their fullness, so that everything that possesses these perfections extrinsically and partially may receive them from somewhere, otherwise we come to the same absurdity which we saw in the last article—that of a potentiality causing its own actuality. An absence of perfection cannot cause actual perfection, any more than the acorn can simultaneously be the oak tree. If in created things these perfections are only extrinsic, received from somewhere else, they can only be received from where they are possessed in their fullness. There must be some entity that does not have a degree of goodness, a degree of beauty, a degree of truth, a degree of life, a degree of existence—but which intrinsically is goodness, is beauty, is truth, is life, is existence itself. Moreover, where each unlimited perfection is possessed in their fullness, goodness is beauty is truth is life is existence. That which is intrinsically perfect is intrinsically simple, not composed of parts, but simply is. This being of absolute perfection is what we call God.
(I owe a great debt in writing this article, and finally coming to even a meagre understanding of the Fourth Way, to the late Thomistic scholar, Fr. Walter Farrell, OP, and his explanation in the first volume of his Companion to the Summa. New York: Sheed & Ward, 1945.)
(Category: Theology Proper: God in general.)