Faith is by its nature a commitment, and without firmness there is no commitment. The biblical idea of faith is clearly opposed to doubt, as appears from the story of Zachary (Luke 1: 18-20) and the words of the risen Jesus to His bewildered disciples (Luke 24: 38; John 20:27). As a decision arising from the very center of the person, faith engages a man totally to the One who can command his full devotion. It therefore surpasses in existential weight those relatively superficial assents to general, abstract or inconsequential truths in which one is not personally involved. In this sense faith requires certitude.
The Catholic is committed by his faith not simply, as all Christians are, to God’s self-giving in Christ, but to a church that claims power to pronounce decisively on doctrinal questions. Adherence to the church implies acceptance of all its dogmas.