In Jesus Christ, the whole of God's truth has been made manifest. "Full of grace and truth," he came as the "light of the world," he is the Truth. "Whoever believes in me may not remain in darkness." The disciple of Jesus continues in his word so as to know "the truth [that] will make you free" and that sanctifies. To follow Jesus is to live in "the Spirit of truth," whom the Father sends in his name and who leads "into all the truth." To his disciples Jesus teaches the unconditional love of truth: "Let what you say be simply 'Yes or No.'"
Source: Catechism of the Catholic Church (Vatican.va)