Called to salvation through faith in Jesus Christ, “the true light that enlightens everyone” (Jn 1:9), people become “light in the Lord” and “children of light” (Eph 5:8), and are made holy by “obedience to the truth” (1 Pet 1:22).

This obedience is not always easy. As a result of that mysterious original sin, committed at the prompting of Satan, the one who is “a liar and the father of lies” (Jn 8:44), man is constantly tempted to turn his gaze away from the living and true God in order to direct it towards idols (cf. 1 Thes 1:9), exchanging “the truth about God for a lie” (Rom 1:25). Man’s capacity to know the truth is also darkened, and his will to submit to it is weakened. Thus, giving himself over to relativism and scepticism (cf. Jn 18:38), he goes off in search of an illusory freedom apart from truth itself.

But no darkness of error or of sin can totally take away from man the light of God the Creator. In the depths of his heart there always remains a yearning for absolute truth and a thirst to attain full knowledge of it. This is eloquently proved by man’s tireless search for knowledge in all fields. It is proved even more by his search for the meaning of life. The development of science and technology, this splendid testimony of the human capacity for understanding and for perseverance, does not free humanity from the obligation to ask the ultimate religious questions. Rather, it spurs us on to face the most painful and decisive of struggles, those of the heart and of the moral conscience.

2. No one can escape from the fundamental questions: What must I do? How do I distinguish good from evil? The answer is only possible thanks to the splendour of the truth which shines forth deep within the human spirit, as the Psalmist bears witness: “There are many who say: ‘O that we might see some good! Let the light of your face shine on us, O Lord’ ” (Ps 4:6).

The light of God’s face shines in all its beauty on the countenance of Jesus Christ, “the image of the invisible God” (Col 1:15), the “reflection of God’s glory” (Heb 1:3), “full of grace and truth” (Jn 1:14). Christ is “the way, and the truth, and the life” (Jn 14:6). Consequently the decisive answer to every one of man’s questions, his religious and moral questions in particular, is given by Jesus Christ, or rather is Jesus Christ himself, as the Second Vatican Council recalls: “In fact,it is only in the mystery of the Word incarnate that light is shed on the mystery of man. For Adam, the first man, was a figure of the future man, namely, of Christ the Lord. It is Christ, the last Adam, who fully discloses man to himself and unfolds his noble calling by revealing the mystery of the Father and the Father’s love.”