God speaks to us through His Church. We all need two conversions. We need to be converted from sin and take Christ for our Saviour, and to be converted to the Church and have her for our Mother. If a person has only experienced one of these operations he is only a half converted man.
Mother Church, like any other mother, expects her young children whom she gathers about her knees and teaches them her Catechism, to believe what she says, because she sits in the seat of authority and is wiser than they. But with true solicitude for their welfare, she desires them not to remain in the infant class, and believe merely because she says so, but to exercise their own powers of reason and understanding and come to see that her teaching is true for themselves. So in corroboration of her teaching she points them to the Holy Scriptures and Tradition. “If any one wishes,” says St. Vincent, “to fortify himself with the Catholic faith” (notice he does not say demonstrate the truth of it), “he must do so by the authority of the Divine Law and the tradition of the Catholic Church.”
–Bishop Charles Grafton, Catholicity and the Vincentian Rule from The Works of the Rt. Rev. Charles C. Grafton, Volume 6 (B. Talbot Rogers ed., New York: Longmans, Green, 1914), p. 184