Dale Tuggy tentatively characterizes Lukas Novak's position on the Trinity as an example of negative mysterianism. This I believe is a mistake. But it depends on what we mean by 'negative mysterianism.' Drawing upon what Tuggy says in his Trinity entry in the Stanford Encyclopedia of Philosophy, let us try to understand what mysterianism is in its negative and positive varieties.
A. The Problem. We first remind ourselves what the problem is. To put it simply in a 'binitarian' form, the problem is to understand how the following propositions can all be true:
1. The Father is not the Son.
2. The Father is God.
3. The Son is God.
4. There is only one God.
It is obvious that if in each sentence the 'is' is the 'is' of absolute numerical identity, then the quartet of propositions is inconsistent. The conjunction of (2) and (3) by the transitivity of identity entails the negation of (1). The conjunction of (1), (2), and (3) entails the negation of (4).
B. Positive Mysterianism. The response of the positive mysterian to the inconsistency is that, in Tuggy''s words:
. . . the trinitarian doctrine can't be understood because of an abundance of content. [. . .] So while we grasp the meaning of its individual claims, taken together they seem inconsistent, and so the conjunction of them is not understandable . . . . The positive mysterian holds that the human mind is adequate to understand many truths about God, although it breaks down at a certain stage, when the most profound divinely revealed truths are entertained. Sometimes an analogy with recent physics is offered; if we find mysteries (i.e., apparent contradictions) there, such as light appearing to be both a particle and a wave, why should we be shocked to find them in theology?
The position of the positive mysterian seems to be the following. The Trinity doctrine is true and therefore consistent in reality despite the fact that it appears to us (and presumably must appear to us given our cognitive limitations) as inconsistent and therefore as necessarily false. Thus positive mysterianism is not to be confused with dialetheism about the Trinity which is the doctrine that there are some true contradictions and that the Trinity doctrine is one of them. The positive mysterian is not saying that the doctrine is a true contradiction; what he maintains is that in itself it is both true and noncontradictory: it only appears to us as contradictory. It is a mystery in the sense of a merely apparent contradiction.
C. Critique. Positive mysterianism seems to entail the view that inconceivability does not entail impossibility. For it implies that the conjunction of (1)-(4), though inconceivable (i.e., not thinkable without contradiction) is true and therefore possible. That conceivability does not entail possibility is old hat. But that inconceivability does not entail impossibility is an innovation that should give us pause.
Why can't I be a positive mysterian about round squares? I cannot conceive of something that is both round and not round at the same time, in the same respect, and in the same sense of 'round.' Normally this inconceivability would be taken as definitive proof of the impossibility of round squares. But if positive mysterianism is true, then the inference fails. For what positive mysterianism countenances is the 'possibility' that a proposition which after due reflection and by all normal tests appears contradictory is in reality not contradictory. So it could be that -- it is epistemically possible that -- round squares are possible and actual. And similarly for an infinity of impossibilia. This seems to be a reductio ad absurdum of positive mysterianism.
Perhaps I will be told that positive mysterianism applies only to the Trinity and the Incarnation. But this restriction of the strategy would be ad hoc and unmotivated. if it works for the Trinity, then it should work across the board. But if it is rigged solely to save the theological doctrines in question, then one's labor is lost. One might as well just dogmatically affirm the two doctrines and not trouble one's head over philosophical justification. Just say: I accept the doctrines and that's that!
Or perhaps I will be told that God is incomprehensible and that the divine incomprehensibility is what warrants the acceptance as true of apparent contradictions. But God cannot be all that incomprehensible if we are able to know that the Father is God,the Son is God, the Father is not the Son, the Son is Jesus, etc. If these propositions are inconsistent when taken together how can unknown and unknowable facts about God remove the contradiction? The contradiction p & ~p cannot be removed by adducing q, r, s, etc. Conceivability can be nullified by the addition of further information; inconceivability, however, cannot be nullified by the addition of further information.
D. Negative Mysterianism. Among the senses of 'mystery' distinguished by Tuggy are the following: " an unintelligible doctrine, the meaning of which can't be grasped…. a truth which one should believe even though it seems, even after careful reflection, to be impossible and/or contradictory and thus false." Tuggy then tells us that "We here call those who call the Trinity a mystery in the fourth sense “negative mysterians” and those who call it a mystery in the fifth sense 'positive mysterians'."
E. Critique. I don't think we need to waste many words on negative mysterianism. If the Trinity is an unintelligible doctrine, then there is nothing for me to wrap my mind around: there is no proposition to entertain, and so no proposition to accept or reject. If it is just a mass of verbiage to which no clear sense can be attached, then the question of its truth or falsity cannot even arise.
F. Novak's View. If I understand Novak's view, it is certainly not a form of mysterianism. For he thinks that if we make the right metaphysical distinctions we will be able to see that the doctrine is noncontradictory. But I'll leave it to him to explain himself more thoroughly.