There is a certain view among Christian philosophers that in order to be justified in one's belief in Christianity one must have studied the best philosophical arguments and come to the conclusion of Christianity through a process of discursive reasoning. Call this "religious evidentialism." The obvious problem is that this would seem to consign anyone who doesn't come to belief in God by studying the arguments into the class of epistemically "unjustified" believers. And that seems to be most believers. I don't think Aquinas would endorse this at all, and I think we can produce a good argument for thinking why this is not the case, on Thomistic grounds:
If this evidentialist approach is right, and most people are unjustified in their belief in Christianity because they didn't study arguments, then at least on a Thomistic view these people are to that extent intellectually failing because their cognitive faculties are failing in some respect and they intentionally act contrary to them. Moreover, to the extent they grow in faith, to the same extent do they grow in being unjustified in their beliefs, and thus grow in intellectual vice. But if Thomism is true, grace perfects nature, and does not destroy or act contrary to it. God doesn't make us do evil things in the process of salvation. He doesn't destroy our nature, but perfects it, i.e. sanctifies us (and on the Thomistic view this is the same as to justify us, in the theological sense). So it can't be true that those faithful who have not studied the arguments are unjustified in their beliefs.
This may provide some warrant for thinking something like Alvin Plantinga's picture of religious epistemology is correct.