In the same way, faith is required of us.
As stated above (Article 3, discussed here) a movement of free-will is required for the justification of the ungodly, inasmuch as man's mind is moved by God. Now God moves man's soul by turning it to Himself according to Psalm 84:7 (Septuagint): "Thou wilt turn us, O God, and bring us to life." Hence for the justification of the ungodly a movement of the mind is required, by which it is turned to God. Now the first turning to God is by faith, according to Hebrews 11:6: "He that cometh to God must believe that He is." Hence a movement of faith is required for the justification of the ungodly. [ST I-II, Q113, A4]
This faith, however, is not mere natural knowledge of God, but rather the knowledge of God that comes by faith:
By natural knowledge a man is not turned to God, according as He is the object of beatitude and the cause of justification. Hence such knowledge does not suffice for justification. [ibid., ad 2]
But if natural knowledge is insufficient, then only a God-given knowledge could be. Hence that faith which is required of us is a gift from God, just as St. Paul says in Eph. 2:8: "For by grace you are saved through faith: and that not of yourselves, for it is the gift of God."
So we see once again that we are entirely dependent upon God for our salvation; it is not something that we can earn on our own merits. Those who say that the Catholic Gospel is "works-based" are misinformed.