Not too long ago on a post on Fr. Aidan Kimel’s blog, there was a dispute in the comments about whether or not it is irrationalist to claim that the Trinity is an unspeakable mystery or “fundamentally unthinkable.”
My own opinion is that it depends on what one means by “fundamentally unthinkable.” I certainly agree that it is wrong and irrationalist when it is practically given as a concession to those arguing the Trinity is contradictory. However, “fundamentally unthinkable” can also be used to mean that, while the doctrine can be shown to be not logically contradictory, nobody can fully understand it in this life. This is certainly not irrationalist, because it requires arguments that the doctrine is not a contradiction, and arguments that our minds cannot perfectly comprehend God as he is. This position, and these two groups of arguments, are found abundantly in tradition, as I will try to show below.
To start with the first group of arguments, as far as I know, no Church Father ever conceded that the Trinity was contradictory. Rather, it was very common to give analogies for it to help people see that it was not absurd. The most effective of these, in my view, is the psychological analogy. It is found in St. Augustine’s De Trinitate (book IX). Thomas Aquinas frequently used a more developed form of it. He states it most concisely in chapters 3-4 of De Rationibus Fidei. Here he likens the Father to an intellect, and the Son to a thought/concept in the intellect. Even this far, one can sort of gets the idea: I am me, but my thoughts are also me, yet I am not my thoughts, but still there are not two of me, only one. But Aquinas points out that in us humans, our thoughts are accidentally part of us, but “in God understanding is not different from his being. Consequently the word which is conceived in his intellect is not something accidental to him or alien from his nature but, by the very fact that it is a word, it must be coming forth from another and must be a likeness of its source.” In chapter 4, Aquinas argues similarly concerning the Holy Spirit, likening it to God’s love. Quite similar arguments are found in St. John of Damascus, St. Symeon the New Theologian, and St. Gregory Palamas. St. Gregory’s version I’ve posted before. St. Symeon the New Theologian’s version I found today in the library:
Just as, when the intellect begets speech, the will of the soul makes it known to listeners either by voice or in writing, like something common to these two parties – and it is clear that these parties are neither confused nor divided into three, but the three are seen or conceived together in each oher, in the one essence and one will -, likewise, regarding the holy, consubstantial, and indivisible Trinity, conceive and profess with piety that the Father begets without speaking God the Word, whom he had in him in the beginning, whom he keeps begotten without division and above all speech, that the Son is begotten all while being always inseparably near the Father who begets him without departing from him, that the Holy Spirit proceeds from the Father all while being of the same nature as the consubstantial Father and Son, one with them, adored and glorified with them by all living.
(Traités théologiques, II, lines 191-205, rough translation by me from Sources Chrétiennes 122)
And St. John of Damascus’s arguments in On the Orthodox Faith, chapters 6-7, is very similar to the summary I gave above of Aquinas’s argument. With these examples alone (not to mention other traditional analogies for the Trinity), I think it is clear that defending the reasonableness of the doctrine of the Trinity is a common tradition found in both East and West.
It is also clear that tradition has also defended the incomprehensibility of God. Augustine, the Cappadocian Fathers, John Chrysostom, Maximus the Confessor, Dionysius the Areopagite, Thomas Aquinas, Gregory Palamas – all agree in supporting so-called apophatic theology. Aquinas is known for saying in the Summa, “We cannot know what God is, but only what He is not.” In the 150 Chapters, chapter 123, St. Gregory Palamas clarifies what it means to say that we can only make negative statements about God:
Apophatic theology does not contradict nor does it deny cataphatic theology; rather, with respect to cataphatic statements about God, it shows that they are true and are made in an orthodox manner, and that God does not possess these things as we do. For example, God possesses knowledge of beings and we too possess this in some cases, but our knowledge refers to things in the present and in the past, whereas God’s does not, for he knows these no less even prior to their coming to be. Thus, the man who says that God does not know beings as such does not contradict one who says that God does know beings and knows them as such. There is a cataphatic theology which has the force of apophatic theology; as when someone says all knowledge is applied to some object, namely, the thing known, but God’s knowledge is not applied to any object, for in that very regard he says that God does not know beings as such and he does not possess knowledge of beings, that is, as we do. In this way God is referred to as non-being in a transcendent sense. But one who says this for the purpose of showing that those who say God exists are not speaking correctly is clearly not using apophatic theology in a transcendent sense but rather in the sense of deficiency to the effect that God does not exist at all. This is the acme of impiety, suffered alas by those who attempt through apophatic theology to deny that God possess both an uncreated substance and energy.
In other words, we are not wrong to make positive statements about God, but these positive statements are analogical. It is rightly said that God possesses knowledge, but it is also rightly said that God does not possess knowledge, since although God does possess knowledge, he possesses it in a different way than we do. St. Augustine has a nice passage relating to analogy in one of his letters (Ep., 7.3.6):
Therefore it is possible for the mind, by taking away, as has been said, some things from objects which the senses have brought within its knowledge, and by adding some things, to produce in the exercise of imagination that which, as a whole, was never within the observation of any of the senses; but the parts of it had all been within such observation, though found in a variety of different things: e.g., when we were boys, born and brought up in an inland district, we could already form some idea of the sea, after we had seen water even in a small cup; but the flavour of strawberries and of cherries could in no wise enter our conceptions before we tasted these fruits in Italy.
It seems to me that God’s understanding is more like the example given of the cup of water and the sea: since we ourselves have understanding, we can easily form a (very rough) notion of what God’s understanding is like. God’s simplicity, however, is a bit more like the example of the fruits: since, unlike God, our human nature is materially divided into different hypostases, we have much greater difficulty of imagining God’s simplicity, where the divine nature is in three undivided hypostases. This helps us understand why we have a harder time grasping God’s oneness despite his various real distinctions than we do when grasping the notion that God has ideas. Therefore the Christian is fully justified in saying that, although we can show that the Trinity is not contradictory, we still should expect not to grasp it fully in this life.
Returning, finally, to the dispute mentioned at the beginning of this post, I would have to answer that it is only right to say that the Trinity is “fundamentally unthinkable” if by that phrase we mean only that us humans in our current state cannot think of the Trinity. Anything more I think would be irrationalist. After having taken a brief look at the book that started the debate, I think the author’s position generally agrees with what I have said above, although I think he greatly exaggerates John of Damascus’s apophaticism.