Classically speaking, there are some truths about God that can be known, or known partially, or grasped, or grasped partially, by reasoned reflection on general revelation. These truths are usually grouped under the domain of natural theology: for example, that there is only one God (monotheism), that he is not a composite being (divine simplicity), that he is infinite, that he is eternal, that he is unchangeable, and so on. Very often, of course, our reasonings go astray and need to be corrected by further divine revelation, such that the truths of nature are frequently better perceived in hindsight–as things we should have known by nature. “Aha! I see now how this was evident all along.” And yet thinkers such as Plato and Aristotle often did arrive at some of these truths, or some aspects of these truths, without special revelation.
There are other truths that, in the view of the majority of Christian thinkers (though not of all Christian thinkers), can only be arrived at by means of special revelation in Scripture. The threeness of the divine Godhead is one of these truths. The majority report of the Christian tradition posits that human reason would never work its way to this conclusion without further divine revelation. Even if one thinks that there are vestigia Trinitatis, “traces of the Trinity,” in the natural world, or in the human mind, or wherever, no one would have deduced that the one, simple God is also triune. Note that this is different from “deducing” three gods; many have obviously “deduced” a multiplicity of gods in control of the world. But no one, says the majority report, would have deduced that the one God is also three, Father, Son, and Holy Spirit.
What I have been calling the “majority report” is the view that Dante puts forward in Purgatorio 3. Not only so, but he puts it in the mouth of his pagan paragon, Vergil (we should remark emphatically at this point that Vergil was not a Christianus sine Christo for Dante, as he was for many other Christians). 1 Vergil considers it a mark of folly to think God’s simultaneous oneness and threeness could be “traced” by human reason, and, further, that it was the folly of hoping for too much from reason alone that brought those archetypal philosopher mentioned above, Plato and Aristotle, to grief. This revelation, moreover, is focused in Jesus Christ, the incarnate Son. If we could have understood God perfectly on our own, there was no reason for Christ to come. For Dante, that is, the revelation of Christ is ordered to the knowledge of the Trinity. 2 These mysteries are beyond us; we should be content to know that these truths of God are so (quia), even if we cannot know why.
Thus Vergil says:
“A sofferir tormenti, caldi e geli
simili corpi la Virtù disponesimili co
è chi spera che nostra ragione
possa trascorrer la infinita via
che tiene una sustanza in tre persone.
State contenti, umana gente, al quia;
ché, se potuto aveste veder tutto,
mestier non era parturir Maria;
e disïar vedeste sanza frutto
tai che sarebbe lor disio quetato,
ch’etternalmente è dato lor per lutto:
io dico d’Aristotile e di Plato
e di molt’ altri”; e qui chinò la fronte,
e più non disse, e rimase turbato.
‘The Power that fits bodies like ours
to suffer torments, heat, and cold
does not reveal the secret of its working.
‘Foolish is he who hopes that with our reason
we can trace the infinite path
taken by one Substance in three Persons.
‘Be content, then, all you mortals, with the quia,
for could you, on your own, have understood,
there was no need for Mary to give birth,
‘and you have seen the fruitless hope of som,
whose very longing, unfulfilled,
now serves them with eternal grief–
‘I speak of Aristotle and of Plato
and of many others.’ And here he lowered his brow,
said nothing more, and seemed perturbed. (Purgatorio 3.31-25, tr. R. Hollander and J. Hollander)
In his notes on the passage, Robert Hollander quotes Benvenuto da Imola’s paraphrase with respect to the idea of knowing “that” even if we do not know “why”: sufficiat vobis credere quia sic est, et non quaerere propter quid est (“Let it be sufficient for you to believe that something is so, and not to seek for what reason something is so”). This advice is obviously of limited applicability, but it is intended to be so. It does not apply to everything, but only to certain properly theological truths. If philosophy is the search for causes (in fact, it is certainly more than this, though it is equally certainly not less), what Dante and Benvenuto da Imola intend to do is to remove certain theological truths from the realm of human reason. Though this move may seem superficially irrationalist, it is not: it is rather a function of divine incomprehensibility. Recall that the scope of the injunction is limited: human reason is sufficiently serviceable in very many respects; Dante and Benvenuto only mean to say that there are truths about God that are beyond reason, though not in contradiction to it. It is a gloss, in other words, on something like Psalm 139.6: “Such knowledge is too wonderful for me; it is high, I cannot attain unto it” (KJV).