Catechism of the Catholic Church: Article 8:The Eighth Commandment
Part 3. Life in Christ
Section 2
Chapter 2. "You Shall Love Your Neighbor as Yourself"
Article 8
You shall not bear false witness against your neighbor.
It was said to the men of old, "You shall not swear falsely, but shall perform to the Lord what you have sworn."
2464The eighth commandment forbids misrepresenting the truth in our relations with others. This moral prescription flows from the vocation of the holy people to bear witness to their God who is the truth and wills the truth. Offenses against the truth express by word or deed a refusal to commit oneself to moral uprightness: they are fundamental infidelities to God and, in this sense, they undermine the foundations of the covenant.
I. Living in the Truth
2465The Old Testament attests that God is the source of all truth. His Word is truth. His Law is truth. His "faithfulness endures to all generations." Since God is "true," the members of his people are called to live in the truth.
2466In 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.'"
2467Man tends by nature toward the truth. He is obliged to honor and bear witness to it: "It is in accordance with their dignity that all men, because they are persons . . . are both impelled by their nature and bound by a moral obligation to seek the truth, especially religious truth. They are also bound to adhere to the truth once they come to know it and direct their whole lives in accordance with the demands of truth."
2468Truth as uprightness in human action and speech is called truthfulness, sincerity, or candor. Truth or truthfulness is the virtue which consists in showing oneself true in deeds and truthful in words, and in guarding against duplicity, dissimulation, and hypocrisy.
2469"Men could not live with one another if there were not mutual confidence that they were being truthful to one another." The virtue of truth gives another his just due. Truthfulness keeps to the just mean between what ought to be expressed and what ought to be kept secret: it entails honesty and discretion. In justice, "as a matter of honor, one man owes it to another to manifest the truth."
2470The disciple of Christ consents to "live in the truth," that is, in the simplicity of a life in conformity with the Lord's example, abiding in his truth. "If we say we have fellowship with him while we walk in darkness, we lie and do not live according to the truth."
II. To Bear Witness to the Truth
2471Before Pilate, Christ proclaims that he "has come into the world, to bear witness to the truth." The Christian is not to "be ashamed then of testifying to our Lord." In situations that require witness to the faith, the Christian must profess it without equivocation, after the example of St. Paul before his judges. We must keep "a clear conscience toward God and toward men."
2472The duty of Christians to take part in the life of the Church impels them to act as witnesses of the Gospel and of the obligations that flow from it. This witness is a transmission of the faith in words and deeds. Witness is an act of justice that establishes the truth or makes it known.
All Christians by the example of their lives and the witness of their word, wherever they live, have an obligation to manifest the new man which they have put on in Baptism and to reveal the power of the Holy Spirit by whom they were strengthened at Confirmation.
2473Martyrdom is the supreme witness given to the truth of the faith: it means bearing witness even unto death. The martyr bears witness to Christ who died and rose, to whom he is united by charity. He bears witness to the truth of the faith and of Christian doctrine. He endures death through an act of fortitude. "Let me become the food of the beasts, through whom it will be given me to reach God."
2474The Church has painstakingly collected the records of those who persevered to the end in witnessing to their faith. These are the acts of the Martyrs. They form the archives of truth written in letters of blood:
Neither the pleasures of the world nor the kingdoms of this age will be of any use to me. It is better for me to die [in order to unite myself] to Christ Jesus than to reign over the ends of the earth. I seek him who died for us; I desire him who rose for us. My birth is approaching. . .
I bless you for having judged me worthy from this day and this hour to be counted among your martyrs. . . . You have kept your promise, God of faithfulness and truth. For this reason and for everything, I praise you, I bless you, I glorify you through the eternal and heavenly High Priest, Jesus Christ, your beloved Son. Through him, who is with you and the Holy Spirit, may glory be given to you, now and in the ages to come. Amen.