The view that St. Thomas should be our model for our understanding of the relationship between faith and reason is a commonplace in Thomistic studies and in Catholic philosophy and theology in general. But what exactly does he say about the ways in which reason suppors theology in its methodology?
Well, lately I've been delving into the topic of theological methodology from a Thomistic perspective. Normally, when I want to research a topic thoroughly in St. Thomas, I usually begin by searching the Index Thomisticus.
Here are three texts that I found in St. Thomas' corpus that are particularly relevant to the topic.
1) One important text was Summa contra gentiles, Book 1, ch. 4:
|Caput 4||Chapter 4|
|Quod veritas divinorum ad quam naturalis ratio pertingit|
convenienter hominibus credenda proponitur
|THAT THE TRUTH ABOUT GOD TO WHICH THE NATURAL REASON REACHES|
IS FITTINGLY PROPOSED TO MEN FOR BELIEF
|Duplici igitur veritate divinorum intelligibilium existente, una ad quam rationis inquisitio pertingere potest, altera quae omne ingenium humanae rationis excedit, utraque convenienter divinitus homini credenda proponitur.|
Hoc autem de illa primo ostendendum est quae inquisitioni rationis pervia esse potest: ne forte alicui videatur, ex quo ratione haberi potest, frustra id supernaturali inspiratione credendum traditum esse.
| Since, therefore, there exists a twofold truth concerning the divine being, one to which the inquiry of the reason can reach, the other which surpasses the whole ability of the human reason, it is fitting that both of these truths be proposed to man divinely for belief.|
This point must first be shown concerning the truth that is open to the inquiry of the reason; otherwise, it might perhaps seem to someone that, since such a truth can be known by the reason, it was uselessly given to men through a supernatural inspiration as an object of belief.
But these are not technically "uses of reason" in theology, but rather a "twofold truth" (duplex veritas) concerning what can be known in about divine things: one which can be attained by reason and another that exceeds reason, both of which needed to be revealed to man by God, but for different reasons. The first of these kinds of truth (which in another text he calls the praeambula fidei) are properly the object of philosophy, whereas the latter (the articuli fidei) can only be studied by theology. The first may also be studied by theology, and in this sense we have two distinct truths which theology can study: the preambles and the articles. And therefore this 'twofold truth' does imply a twofold use of reason in theology, but this is not explicitly what St. Thomas is addressing, and there seems to be an important difference here between what he is saying and what I've drawn out from what he's saying.
2) Another text I found is Summa theologiae Ia, q. 32, a. 1, ad 2:
|Ad secundum dicendum quod ad aliquam rem dupliciter inducitur ratio. Uno modo, ad probandum sufficienter aliquam radicem, sicut in scientia naturali inducitur ratio sufficiens ad probandum quod motus caeli semper sit uniformis velocitatis. Alio modo inducitur ratio, non quae sufficienter probet radicem, sed quae radici iam positae ostendat congruere consequentes effectus, sicut in astrologia ponitur ratio excentricorum et epicyclorum ex hoc quod, hac positione facta, possunt salvari apparentia sensibilia circa motus caelestes, non tamen ratio haec est sufficienter probans, quia etiam forte alia positione facta salvari possent. Primo ergo modo potest induci ratio ad probandum Deum esse unum, et similia. Sed secundo modo se habet ratio quae inducitur ad manifestationem Trinitatis, quia scilicet, Trinitate posita, congruunt huiusmodi rationes; non tamen ita quod per has rationes sufficienter probetur Trinitas personarum. Et hoc patet per singula. Bonitas enim infinita Dei manifestatur etiam in productione creaturarum, quia infinitae virtutis est ex nihilo producere. Non enim oportet, si infinita bonitate se communicat, quod aliquid infinitum a Deo procedat, sed secundum modum suum recipiat divinam bonitatem. Similiter etiam quod dicitur, quod sine consortio non potest esse iucunda possessio alicuius boni, locum habet quando in una persona non invenitur perfecta bonitas; unde indiget, ad plenam iucunditatis bonitatem, bono alicuius alterius consociati sibi. Similitudo autem intellectus nostri non sufficienter probat aliquid de Deo, propter hoc quod intellectus non univoce invenitur in Deo et in nobis. Et inde est quod Augustinus, super Ioan., dicit quod per fidem venitur ad cognitionem, et non e converso.||Reply to Objection 2: Reason may be employed in two ways to establish a point: firstly, for the purpose of furnishing sufficient proof of some principle, as in natural science, where sufficient proof can be brought to show that the movement of the heavens is always of uniform velocity. Reason is employed in another way, not as furnishing a sufficient proof of a principle, but as confirming an already established principle, by showing the congruity of its results, as in astrology the theory of eccentrics and epicycles is considered as established, because thereby the sensible appearances of the heavenly movements can be explained; not, however, as if this proof were sufficient, forasmuch as some other theory might explain them. In the first way, we can prove that God is one; and the like. In the second way, reasons avail to prove the Trinity; as, when assumed to be true, such reasons confirm it. We must not, however, think that the trinity of persons is adequately proved by such reasons. This becomes evident when we consider each point; for the infinite goodness of God is manifested also in creation, because to produce from nothing is an act of infinite power. For if God communicates Himself by His infinite goodness, it is not necessary that an infinite effect should proceed from God: but that according to its own mode and capacity it should receive the divine goodness. Likewise, when it is said that joyous possession of good requires partnership, this holds in the case of one not having perfect goodness: hence it needs to share some other's good, in order to have the goodness of complete happiness. Nor is the image in our mind an adequate proof in the case of God, forasmuch as the intellect is not in God and ourselves univocally. Hence, Augustine says (Tract. xxvii. in Joan.) that by faith we arrive at knowledge, and not conversely.|
This text does present a distinction between uses of reason: one demonstrative, the other 'manifestative' (as Garrigou-Lagrange calls it, stating that we use reason this way when dealing with things that non possunt nec probari nec improbari, sed cum probabilitate suadentur et sola fide cum certitudine tenentur).
So I'm assuming that we get the three "uses of reason" by combining this distinction in ST Ia, q. 32, a. 1 ad 2 with the distinction in SCG I.4. Thus, we have:
(a) reason as demonstrating divine things independently from revelation,
(b) reason as demonstrating divine things on the basis of revelation as its starting point, and
(c) reason, not as demonstrating, but only 'making manifest' divine things.
3) Super De Trinitate, pars 1 q. 2 a. 3 co. 3 (text borrowed from The Logic Museum):
|Sic ergo in sacra doctrina philosophia possumus tripliciter uti.||Thus, in sacred doctrine we are able to make a threefold use of philosophy:|
|Primo ad demonstrandum ea quae sunt praeambula fidei, quae necesse est in fide scire, ut ea quae naturalibus rationibus de Deo probantur, ut Deum esse, Deum esse unum et alia huiusmodi vel de Deo vel de creaturis in philosophia probata, quae fides supponit.||1. First, to demonstrate those truths that are preambles of faith and that have a necessary place in the science of faith. Such are the truths about God that can be proved by natural reason—that God exists, that God is one; such truths about God or about His creatures, subject to philosophical proof, faith presupposes.|
|Secundo ad notificandum per aliquas similitudines ea quae sunt fidei, sicut Augustinus in libro de Trinitate utitur multis similitudinibus ex doctrinis philosophicis sumptis ad manifestandum Trinitatem.||2. Secondly, to give a clearer notion, by certain similitudes, of the truths of faith, as Augustine in his book, De Trinitate, employed any comparisons taken from the teachings of the philosophers to aid understanding of the Trinity.|
|Tertio ad resistendum his quae contra fidem dicuntur sive ostendendo ea esse falsa sive ostendendo ea non esse necessaria.||3. In the third place, to resist those who speak against the faith, either by showing that their statements are false, or by showing that they are not necessarily true.|
Here we have a slightly different distinction. We do find some version of elements (a) and (c), but we also have a brand new element, the third and last one in the text, which consists in (d) refuting the arguments of those who argue against the faith, by showing that their arguments are either false or non demonstrative. At any rate, if we gather all these texts, it seems we get at least four different uses of reason in theology.
I am not trying to draw any conclusive synthesis here, as this is just a research starting point. I will share more as I continue to work on this topic. In the meantime, compare the above with Garrigou-Lagrange (Reality, Ch. 6), who identifies six "steps" in theological procedure, some of which seem to be identical (or at least reducible) to the ones mentioned above:
Article Two: Steps In Theological Procedure
These steps are pointed out by St. Thomas, first in the first question of the Summa, secondly, more explicitly, when he treats of specific subjects: eternal life, for example, predestination, the Trinity, the mysteries of the Incarnation, the Redemption, the Eucharist, and the other sacraments. We distinguish six such successive procedures.
1. The positive procedure.
2. The analytic procedure.
3. The apologetic procedure.
4. The manifestative procedure.
5. The explicative procedure.
6. The illative procedure.
(a) of truths explicitly revealed.
(b) of truths not explicitly revealed.
(c) of truths virtually revealed.