The other element of the Evangelical Law is secondary: namely, the teachings of faith, and those commandments which direct human affections and human actions. And as to this, the New Law does not justify... Augustine explains this by saying that the letter denotes any writing external to man, even that of the moral precepts such as are contained in the Gospel. Wherefore the letter, even of the Gospel would kill, unless there were the inward presence of the healing grace of faith.In just a few short questions of his magnum opus, the Summa Theologica, Thomas provides a perfect synthesis (yes, I said perfect) of the Catholic view of revelation. The parts I explore with my class include the following from the ‘First Part of the Second Part:’ 98 (6), 100 (a.12), 101 (a.2), 102 (a.2), 103 (4), 106 (4), q. 107 (4), q. 108 (4). You could spend a lot more time on his writing on this subject, but I have found these pieces to be satisfactory. The above quote is from Question 106, Article 2.
I base my presentation of this aspect of the thought of Thomas upon my own experience of coming to faith in the Holy Scriptures. That is my method in my biblical course as well. In light of this, I think that one of the best things Thomas can do for adult believers today is to properly situate the Old Testament with respect to the New Testament. It seems to me that everyone who thinks about Scripture must have these two questions in the back of their minds (if not at the front): why two Testaments? And, what view of them am I suppose to have? In a nutshell, Thomas looks as them as imperfect to perfect, one as preparatory, the other as fulfillment, one as prophetic, the other as thing prophesied... Now, if the OT were to justify, i.e., make one worthy of heaven, it would not be imperfect. The above quote goes one step further, here Thomas tells us that not even the New justifies in a certain sense. He says that the teachings of the Faith and its commandments do not justify! In this he is perfectly consistent, and, indeed, perfectly correct – but what a radical configuration such a position would demand of certain people’s understanding of the Faith!
He tells us that the grace of Christ justifies, nothing else does in any sense, anywhere, in any way, ever. Thus, not even to believe the right thing has one lick to do with your justification.
Soak that in for a second and then let me proceed.
Does this mean that having the right faith is worthless? Far from it. Or, in some sense, close to it. Right faith, maintained in the right way (i.e. as animated by charity), is a fruit of justification, not its cause.
Soak that in for a second.
Nevertheless, do not conclude from this that because you have the right faith (and you think you mean your neighbour well) you are justified. The problem does not first and foremost lie in the difficulty of determining whether your faith is right; it lies primarily with determining whether your faith is animated by charity.