Objection 1. It would seem that faith is not the first of the virtues. For a gloss on Luke 12:4, "I say to you My friends," says that fortitude is the foundation of faith. Now the foundation precedes that which is founded thereon. Therefore faith is not the first of the virtues.
Objection 2. Further, a gloss on Psalm 36, "Be not emulous," says that hope "leads on to faith." Now hope is a virtue, as we shall state further on (17, 1). Therefore faith is not the first of the virtues.
Objection 3. Further, it was stated above (Article 2) that the intellect of the believer is moved, out of obedience to God, to assent to matters of faith. Now obedience also is a virtue. Therefore faith is not the first virtue.
Objection 4. Further, not lifeless but living faith is the foundation, as a gloss remarks on 1 Corinthians 3:11 [Augustine, De Fide et Oper. xvi.]. Now faith is formed by charity, as stated above (Article 3). Therefore it is owing to charity that faith is the foundation: so that charity is the foundation yet more than faith is (for the foundation is the first part of a building) and consequently it seems to precede faith.
Objection 5. Further, the order of habits is taken from the order of acts. Now, in the act of faith, the act of the will which is perfected by charity, precedes the act of the intellect, which is perfected by faith, as the cause which precedes its effect. Therefore charity precedes faith. Therefore faith is not the first of the virtues.
On the contrary, The Apostle says (Hebrews 11:1) that "faith is the substance of things to be hoped for." Now the substance of a thing is that which comes first. Therefore faith is first among the virtues.
I answer that, One thing can precede another in two ways: first, by its very nature; secondly, by accident. Faith, by its very nature, precedes all other virtues. For since the end is the principle in matters of action, as stated above (I-II, 13, 3; I-II, 34, 4, ad 1), the theological virtues, the object of which is the last end, must needs precede all the others. Again, the last end must of necessity be present to the intellect before it is present to the will, since the will has no inclination for anything except in so far as it is apprehended by the intellect. Hence, as the last end is present in the will by hope and charity, and in the intellect, by faith, the first of all the virtues must, of necessity, be faith, because natural knowledge cannot reach God as the object of heavenly bliss, which is the aspect under which hope and charity tend towards Him.
On the other hand, some virtues can precede faith accidentally. For an accidental cause precedes its effect accidentally. Now that which removes an obstacle is a kind of accidental cause, according to the Philosopher (Phys. viii, 4): and in this sense certain virtues may be said to precede faith accidentally, in so far as they remove obstacles to belief. Thus fortitude removes the inordinate fear that hinders faith; humility removes pride, whereby a man refuses to submit himself to the truth of faith. The same may be said of some other virtues, although there are no real virtues, unless faith be presupposed, as Augustine states (Contra Julian. iv, 3).
This suffices for the Reply to the First Objection.
Reply to Objection 2. Hope cannot lead to faith absolutely. For one cannot hope to obtain eternal happiness, unless one believes this possible, since hope does not tend to the impossible, as stated above (I-II, 40, 1). It is, however, possible for one to be led by hope to persevere in faith, or to hold firmly to faith; and it is in this sense that hope is said to lead to faith.
Reply to Objection 3. Obedience is twofold: for sometimes it denotes the inclination of the will to fulfil God's commandments. On this way it is not a special virtue, but is a general condition of every virtue; since all acts of virtue come under the precepts of the Divine law, as stated above (I-II, 100, 2); and thus it is requisite for faith. On another way, obedience denotes an inclination to fulfil the commandments considered as a duty. On this way it is a special virtue, and a part of justice: for a man does his duty by his superior when he obeys him: and thus obedience follows faith, whereby man knows that God is his superior, Whom he must obey.
Reply to Objection 4. To be a foundation a thing requires not only to come first, but also to be connected with the other parts of the building: since the building would not be founded on it unless the other parts adhered to it. Now the connecting bond of the spiritual edifice is charity, according to Colossians 3:14: "Above all... things have charity which is the bond of perfection." Consequently faith without charity cannot be the foundation: and yet it does not follow that charity precedes faith.
Reply to Objection 5. Some act of the will is required before faith, but not an act of the will quickened by charity. This latter act presupposes faith, because the will cannot tend to God with perfect love, unless the intellect possesses right faith about Him.
Source: Summa Theologica (New Advent)