The Council teaches that “the obedience of faith must be given to God who reveals himself”. This brief but dense statement points to a fundamental truth of Christianity. Faith is said first to be an obedient response to God. This implies that God be acknowledged in his divinity, transcendence and supreme freedom. By the authority of his absolute transcendence, God who makes himself known is also the source of the credibility of what he reveals. By faith, men and women give their assent to this divine testimony. This means that they acknowledge fully and integrally the truth of what is revealed because it is God himself who is the guarantor of that truth. They can make no claim upon this truth which comes to them as gift and which, set within the context of interpersonal communication, urges reason to be open to it and to embrace its profound meaning. This is why the Church has always considered the act of entrusting oneself to God to be a moment of fundamental decision which engages the whole person. In that act, the intellect and the will display their spiritual nature, enabling the subject to act in a way which realizes personal freedom to the full. It is not just that freedom is part of the act of faith: it is absolutely required. Indeed, it is faith that allows individuals to give consummate expression to their own freedom. Put differently, freedom is not realized in decisions made against God. For how could it be an exercise of true freedom to refuse to be open to the very reality which enables our self-realization? Men and women can accomplish no more important act in their lives than the act of faith; it is here that freedom reaches the certainty of truth and chooses to live in that truth.
To assist reason in its effort to understand the mystery there are the signs which Revelation itself presents. These serve to lead the search for truth to new depths, enabling the mind in its autonomous exploration to penetrate within the mystery by use of reason’s own methods, of which it is rightly jealous. Yet these signs also urge reason to look beyond their status as signs in order to grasp the deeper meaning which they bear. They contain a hidden truth to which the mind is drawn and which it cannot ignore without destroying the very signs which it is given.
In a sense, then, we return to the sacramental character of Revelation and especially to the sign of the Eucharist, in which the indissoluble unity between the signifier and signified makes it possible to grasp the depths of the mystery. In the Eucharist, Christ is truly present and alive, working through his Spirit; yet, as Saint Thomas said so well, “what you neither see nor grasp, faith confirms for you, leaving nature far behind; a sign it is that now appears, hiding in mystery realities sublime”. He is echoed by the philosopher Pascal: “Just as Jesus Christ went unrecognized among men, so does his truth appear without external difference among common modes of thought. So too does the Eucharist remain among common bread”.
In short, the knowledge proper to faith does not destroy the mystery; it only reveals it the more, showing how necessary it is for people’s lives: Christ the Lord “in revealing the mystery of the Father and his love fully reveals man to himself and makes clear his supreme calling”, which is to share in the divine mystery of the life of the Trinity. — from Fides et Ratio (1998)