Catechism of the Catholic Church

151 For a Christian, believing in God cannot be separated from believing in the One he sent, his "beloved Son", in whom the Father is "well pleased"; God tells us to listen to him. ¹⁸ The Lord himself said to his disciples: "Believe in God, believe also in me." ¹⁹ We can believe in Jesus Christ because he is himself God, the Word made flesh: "No one has ever seen God; the only Son, who is in the bosom of the Father, he has made him known." ²⁰ Because he "has seen the Father", Jesus Christ is the only one who knows him and can reveal him. ²¹