521. What is one's duty toward the truth?Every person is called to sincerity and truthfulness in acting and speaking. Everyone has the duty to seek the truth, to adhere to it and to order one's whole life in accordance with its demands. In Jesus Christ the whole of God's truth has been made manifest. He is "
the truth". Those who follow him live in the Spirit of truth and guard against duplicity, dissimulation, and hypocrisy.
Further reading: CCC 2464-2470, 2504522. How does one bear witness to the truth?
A Christian must bear witness to the truth of the Gospel in every field of his activity, both public and private, and also if necessary, with the sacrifice of his very life. Martyrdom is the supreme witness given to the truth of the faith.
Further reading: CCC 2471-2474, 2505-2506