I read Aquinas and realized that the whole ancient conception of a soul is tied together with the ancient concept of vitalism. Within vitalism you need something to explain why living matter is different than non-living matter, and that something is the presence of a soul! Hey presto, add a few layers of philosophy and divine revelation and you arrive at the Christian immortal soul.
(In this case "god of the gaps" does not refer to the Catholic God himself, but instead it refers specifically to the concept of the soul)
Aquinas, in his Summa, makes a series of assertion-of-fact about souls. Specifically, he claims that the soul explains (or "is the principle of") certain otherwise-unexplained phenomenon.
It doesn't matter how he got there (i.e. whether he was arguing with someone online, or trying to explain catholicism in terms of Aristotle, or if he was just an LLM stochastically putting ink on parchment), the fact is that inventing a supernatural thing that explains a bunch of unexplained phenomenon is precisely what I meant by "god-of-the-gaps style reasoning."
And therein lies my point: the purpose of Aquinas was purely to explain preexisting Catholic theology, using Aristotle as a starting point. He invented nothing.
You can say "the Catholic Church invented the soul to explain [etc]" and then I'd just push it back to Christianity itself, and if you'd concede on that, we'd have resolved my initial argument.
Many Christian theologians attempted to demonstrate the existence of God rationally, so I don't know what about that process would have been considered heretical in its own right. I'd agree that the claim (associated with Deists, for example) that one could have a complete religion based exclusively on reason with no revelation, or that all purported divine revelations are untrustworthy, would have been considered heretical.
The first rabbi who goes the above path - and during his time, his books were often burnt.
It still is, according to Catholicism, which says you must have reason and faith in the divine revelation it claims to preserve, which reveals some aspects of God and reality that we cannot reach or conclude with pure reason alone, such as the Blessed Virgin Mary's Immaculate Conception (BVMIC for short) or the Trinity (T for short).
This is simply not true, and I've quoted the passages from Aquinas that explicitly assert metaphysical differences between living and non-living matter in this very thread.
If you want a tidy introduction to metaphysics of this sort, consider this one [0].
*Assuming by metaphysical you mean formal.
Can you elaborate on how you arrived at this conclusion? There are multiple Popes that have rejected “god-of-the-gaps” explanations instead invoking the idea that science helps one learn more about God, not as a rationale for invoking God where we are ignorant.