I want to suspend my reservations about the doctrine of middle knowledge for the moment in order to explore two interesting (possibly advantageous) consequences for our theology of Revelation which it may have. First of all, we may be able to marry the following two claims: 1) it is impossible without revelation apart from human reason (that is, human reason operating alone) to know that the Trinity is true, and 2) it is possible to deduce by reason without appeal to revelation that God exists and is a Trinity.
In the first place God might know by middle knowledge that across all logically possible worlds in which revelation does not occur, nobody will ever come to know that he is a Trinity (thus, such possible worlds are eliminated by the subjunctive counterfactual, while strictly ‘possible’ they aren’t feasible in light of the counterfactual). Thus God knows that it is not logically possible, in the absence of revelation, that man come to know certain truths. However, this is obviously compatible with the claim that we who live in a world in which God has engaged the human conversation by truly revealing himself might now be able to reason our way to the truth of the Trinity. I note in passing that while this is not, I take it, a legitimate interpretation of what Catholic doctrine says about how the Trinity is a deliverance of revelation not in principle arrived at by the use of the faculty of reason unguided by revelation and faith, still some Medievals held to something not entirely different. For instance Bonaventure would have eagerly agreed that the Trinity was a deliverance of revelation which the human mind unguided by God’s self revelation could never discern in principle, but he also maintained that it can be demonstrated with reason alone to one whose mind/soul is properly disposed by revelation that God is Trinity. See his demonstration here.
As a tangential remark, I think it is interesting to ask whether it is logically feasible for God to create a world of cognizers who could, by natural disposition, think their way to the Trinitarian formulae of faith. One might wonder if it is logically feasible given the Fallen state of the mind of man (presumably all knowledge and right thinking is aided by the Holy spirit, but that is by general grace, and not by special grace). I think it may be. Finally it is worth wondering if, in such worlds, presuming the existence of some such worlds, the people who think their way to the Trinity by natural inclination would ‘know’ that the trinity is true. Even if it were a true justified belief, it isn’t clear, as Gettier shows us, whether one can be said to know anything if their justifications for believing it have nothing to do with the reasons it ‘is’ true. After all this, what is the significance that we live in such a world where it happens (or is as it must be, depending on our conclusions to these aforementioned questions) to be the case that we cannot arrive at a knowledge that the trinity is true without special Grace? ~End of tangent.
Another related consequence may be more specifically for hermeneutics. Consider the infamous Abrahamic episode where Isaac is being offered as a sacrifice to God according to God’s commandment to Abraham. Here we might begin by pointing out that God did not command anything contrary to the moral law, but rather commanded that Abraham ready his son for a sacrifice, and sacrifice his son insofar as the motivation of his act is concerned, but not, obviously, the effect, since then either Abraham did not obey, or God can change. So, God did not demand of Abraham any immoral thing per se. More appropriately we can say that God reveals himself progressively, such that he would at first command Abraham to sacrifice his son, and then later to cease and desist, but in principle God intended to prevent Abraham from sacrificing his own son from the beginning, and thus what God intended by the commandment was an act of the will on the part of Abraham, which was accomplished. This act of the will, then, does not constitute anything immoral insofar as it is considered on it’s own as a sacrifice. We can add to this that God could not have commanded Abraham to do that which his own conscience definitively set itself in opposition to without ambiguity. However, we may be able to lift another insight on the way – that where our moral conscience is not yet properly formed, coming to its maturity, we ought to humble ourselves to revelation and allow it to inform us regardless of what sacrifices it may entail for us (with the promise of clairvoyance in retrospect). I digress though and return to my point which is to note that, on the supposition of middle knowledge, we might say that part of the sufficient reason God revealed himself in the event (and myth) of this episode was to elicit in us, its readers, a great and unsearchable depth of existential struggle in hermeneutics, without which the Church might have otherwise been greatly impoverished. That might qualify as morally sufficient reason for God to allow Abraham to be ready to sacrifice his son. That, though, also clearly requires middle knowledge.