153 When St. Peter confessed that Jesus is the Christ, the Son of the living God, Jesus declared to him that this revelation did not come "from flesh and blood", but from "my Father who is in heaven".24 Faith is a gift of God, a supernatural virtue infused by him. "Before this faith can be exercised, man must have the grace of God to move and assist him; he must have the interior helps of the Holy Spirit, who moves the heart and converts it to God, who opens the eyes of the mind and 'makes it easy for all to accept and believe the truth.'"²⁵

Faith is a human act

154 Believing is possible only by grace and the interior helps of the Holy Spirit. But it is no less true that believing is an authentically human act. Trusting in God and cleaving to the truths he has revealed is contrary neither to human freedom nor to human reason. Even in human relations it is not contrary to our dignity to believe what other persons tell us about themselves and their intentions, or to trust their promises (for example, when a man and a woman marry) to share a communion of life with one another. If this is so, still less is it contrary to our dignity to "yield by faith the full submission of... intellect and will to God who reveals",26 and to share in an interior communion with him.

155 In faith, the human intellect and will co-operate with divine grace: "Believing is an act of the intellect assenting to the divine truth by command of the will moved by God through grace."27

Faith and understanding

156 What moves us to believe is not the fact that revealed truths appear as true and intelligible in the light of our natural reason: we believe "because of the authority of God himself who reveals them, who can neither deceive nor be deceived".28 So "that the submission of our faith might nevertheless be in accordance with reason, God willed that external proofs of his Revelation should be joined to the internal helps of the Holy Spirit."²⁹ Thus the miracles of Christ and the saints, prophecies, the Church's growth and holiness, and her fruitfulness and stability "are the most certain signs of divine Revelation, adapted to the intelligence of all"; they are "motives of credibility" (motiva credibilitatis), which show that the assent of faith is "by no means a blind impulse of the mind".³⁰

157 Faith is certain. It is more certain than all human knowledge because it is founded on the very word of God who cannot lie. To be sure, revealed truths can seem obscure to human reason and experience, but "the certainty that the divine light gives is greater than that which the light of natural reason gives."31 "Ten thousand difficulties do not make one doubt."³²

158 "Faith seeks understanding":33 it is intrinsic to faith that a believer desires to know better the One in whom he has put his faith, and to understand better what He has revealed; a more penetrating knowledge will in turn call forth a greater faith, increasingly set afire by love. the grace of faith opens "the eyes of your hearts"³⁴ to a lively understanding of the contents of Revelation: that is, of the totality of God's plan and the mysteries of faith, of their connection with each other and with Christ, the centre of the revealed mystery. "The same Holy Spirit constantly perfects faith by his gifts, so that Revelation may be more and more profoundly understood."³⁵ In the words of St. Augustine, "I believe, in order to understand; and I understand, the better to believe."³⁶

159 Faith and science: "Though faith is above reason, there can never be any real discrepancy between faith and reason. Since the same God who reveals mysteries and infuses faith has bestowed the light of reason on the human mind, God cannot deny himself, nor can truth ever contradict truth."37 "Consequently, methodical research in all branches of knowledge, provided it is carried out in a truly scientific manner and does not override moral laws, can never conflict with the faith, because the things of the world and the things of faith derive from the same God. the humble and persevering investigator of the secrets of nature is being led, as it were, by the hand of God in spite of himself, for it is God, the conserver of all things, who made them what they are."³⁸

The freedom of faith

160 To be human, "man's response to God by faith must be free, and... therefore nobody is to be forced to embrace the faith against his will. the act of faith is of its very nature a free act."39 "God calls men to serve him in spirit and in truth. Consequently they are bound to him in conscience, but not coerced. . . This fact received its fullest manifestation in Christ Jesus."⁴⁰ Indeed, Christ invited people to faith and conversion, but never coerced them. "For he bore witness to the truth but refused to use force to impose it on those who spoke against it. His kingdom... grows by the love with which Christ, lifted up on the cross, draws men to himself."⁴¹

The necessity of faith

161 Believing in Jesus Christ and in the One who sent him for our salvation is necessary for obtaining that salvation.42 "Since "without faith it is impossible to please (God) " and to attain to the fellowship of his sons, therefore without faith no one has ever attained justification, nor will anyone obtain eternal life 'But he who endures to the end.'"]

Perseverance in faith

162 Faith is an entirely free gift that God makes to man. We can lose this priceless gift, as St. Paul indicated to St. Timothy: "Wage the good warfare, holding faith and a good conscience. By rejecting conscience, certain persons have made shipwreck of their faith."44 To live, grow and persevere in the faith until the end we must nourish it with the word of God; we must beg the Lord to increase our faith;⁴⁵ it must be "working through charity," abounding in hope, and rooted in the faith of the Church.⁴⁶

Faith - the beginning of eternal life

163 Faith makes us taste in advance the light of the beatific vision, the goal of our journey here below. Then we shall see God "face to face", "as he is".47 So faith is already the beginning of eternal life:
When we contemplate the blessings of faith even now, as if gazing at a reflection in a mirror, it is as if we already possessed the wonderful things which our faith assures us we shall one day enjoy.⁴⁸

164 Now, however, "we walk by faith, not by sight";49 we perceive God as "in a mirror, dimly" and only "in part".⁵⁰ Even though enlightened by him in whom it believes, faith is often lived in darkness and can be put to the test. the world we live in often seems very far from the one promised us by faith. Our experiences of evil and suffering, injustice and death, seem to contradict the Good News; they can shake our faith and become a temptation against it.

165 It is then we must turn to the witnesses of faith: to Abraham, who "in hope... believed against hope";51 to the Virgin Mary, who, in "her pilgrimage of faith", walked into the "night of faith"⁵² in sharing the darkness of her son's suffering and death; and to so many others: "Therefore, since we are surrounded by so great a cloud of witnesses, let us also lay aside every weight, and sin which clings so closely, and let us run with perseverance the race that is set before us, looking to Jesus the pioneer and perfecter of our faith."⁵³