18 Part One IN BRIEF 44 Man is by nature and vocation a religious being. Com- ing from God, going toward God, man lives a fully human life only if he freely lives by his bond with God. 45 Man is made to live in communion with God in whom he finds happiness: “When I am completely united to you, there will be no more sorrow or trials; entirely full of you, my life will be complete” (St. Augustine, Conf. 10, 28, 39: PL 32, 795). 46 When he listens to the message of creation and to the voice of conscience, man can arrive at certainty about the existence of God, the cause and the end of every thing. 47 The Church teaches that the one true God, our Creator and Lord, can be known with certainty from his works, by the natural light of human reason (cf. Vati- can Council I, can. 2, § 1: DS 3026). 48 We really can name God, starting from the manifold perfections of his creatures, which are likenesses of the infinitely perfect God, even if our limited language cannot exhaust the mystery. 49 “Without the Creator, the creature vanishes” ( GS 36). This is the reason why believers know that the love of Christ urges them to bring the light of the living God to those who do not know him or who reject him.