but of perfect freedom, and therefore in itself an act of normal obedience to God, and meritorious in its nature. And this act of faith, in which both the intellect and the will have their full and normal exercise, is nevertheless an act not of the natural order, but of the supernatural, and springs from the preventing grace of the Holy Spirit, Who illuminates the intelligence and moves the will. Faith is therefore a gift of God, and a moral duty which may be required of us by the commandment of God.
But inasmuch as the grace of faith is given to man that he may believe the revelation of God, it is co-extensive with that whole revelation. Whatsoever God has revealed, man, when he knows it, is bound to believe. But God has made provision that man should know His revelation, because He has committed it to His Church as the guardian and teacher of truth. Whatsoever, therefore, the Church proposes to our belief as the Word of God, written or unwritten, whether by its ordinary and universal teaching, or by its solemn judgment and definition, we are bound to believe by divine and Catholic faith.
To this end, God has instituted in the world His visible Church, one, universal, indefectible, immutable, ever multiplying; the living witness of the Incarnation, and the sufficient evidence of its own mission to the world. The maximum of extrinsic evidence for the revelation of Christianity is the witness of the Church, considered even as an historical proof; and that extrinsic evidence is not only sufficient to convince a rational nature that Christianity is a Divine revelation, but to convict of
