(This was posted on FB, but I thought I should back it up….)
There are at least three threads to pull on here.
First: ST I-II, q. 89,a . 6 (Whether venial sin can be in anyone with original sin alone). This is a capital text. I would need to go digging through the Salmanticenses and Cajetan. I would think that something also is reflected, more briefly in Billuart.
On this theme, it is useful to consider the thought provoking content on this head in Maritain’s “The Immanent Dialectic of the First Act of Freedom,” in The Range of Reason. He engages the them in relation to the Thomist school. The text, even if touched up here and there, was broadly accepted, from what I recall, by Frs. Labourdette OP and Nicolas OP, both of whom are very safe theologically. (I am getting blue in the face nowadays, though, feeling like I need to defend Maritain all the time because of certain polemicists who like to trot him out as a bogey man for so many post-conciliar ills. I know his works very well, and even where I might differ with him, even on this or that point of politics, I’m not ready to be so dogmatic. Okay, end of potential rant……) There may be something in Journet’s Église du verbe incarné as well…. Just went over to my shelf to look at vol. 2. Yes, indeed. See pages 763-799. This deals with the problem of invincible ignorance in these matters directly.
Second: Look at relevant commentaries on the treatise on faith. In particular, see commentaries on ST II-II, q. 2, a. 5-7; also, related see q. 1, a. 7. Look at Garrigou’s commentary on those texts. I just now ordered Ramirez’s De fide divina, which I really should just have… Moreover, see Labourdette’s recently published, 149-161 and, in particular, the excursus on pages 310 to 355.
Finally, there is the issue, as John noted well, concerning baptism “in voto.” On such sacramental matters, one must always consult Doronzo, for to do otherwise is to court superficial presentism in comparison with his magisterial Thomistic synthesis, which bears witness to how much theological culture has jettisoned. See article 9 (p. 104-134) and ch. 9 as a whole (on baptism by water, fire, and blood).
Also, see Ch. 5 of Hugon’s _Hors d l’église point de salut._