Any moral value has its foundation in truth because good is the manifestation of good. The problem of truth and lie has been considered as having great importance in man’s life of all times. Man is measured by truth. The first lie is the simulation of truth by man himself. Man is tempted by lie and accepts the temptation of denying his ontological truth. Since the man is endowed with freedom, he is self-possession, trusted to him and disposing of him, but he did not offered by him this self-possession, instead he owns it to another. God puts his own infinite freedom in relation with the finite freedom of man. With his sinful presumption of wanting to be like God man has denied the truth of his being. For the modern man, his person has become the trustful point of reality. Lie knows today a collective and public dimension which amplified thanks to the social communications.