Man, tempted by the devil, let his trust in his Creator die in his heart and, abusing his freedom, disobeyed God’s command. This is what man’s first sin consisted of. All subsequent sin would be disobedience toward God and lack of trust in his goodness.
In that sin man preferred himself to God and by that very act scorned him. He chose himself over and against God, against the requirements of his creaturely status and therefore against his own good. Created in a state of holiness, man was destined to be fully “divinized” by God in glory. Seduced by the devil, he wanted to “be like God”, but “without God, before God, and not in accordance with God”.
Scripture portrays the tragic consequences of this first disobedience. Adam and Eve immediately lose the grace of original holiness. They become afraid of the God of whom they have conceived a distorted image – that of a God jealous of his prerogatives.
The harmony in which they had found themselves, thanks to original justice, is now destroyed: the control of the soul’s spiritual faculties over the body is shattered; the union of man and woman becomes subject to tensions, their relations henceforth marked by lust and domination. Harmony with creation is broken: visible creation has become alien and hostile to man. Because of man, creation is now subject “to its bondage to decay”. Finally, the consequence explicitly foretold for this disobedience will come true: man will “return to the ground”, for out of it he was taken. Death makes its entrance into human history.
After that first sin, the world is virtually inundated by sin There is Cain’s murder of his brother Abel and the universal corruption which follows in the wake of sin. Likewise, sin frequently manifests itself in the history of Israel, especially as infidelity to the God of the Covenant and as transgression of the Law of Moses. and even after Christ’s atonement, sin raises its head in countless ways among Christians. Scripture and the Church’s Tradition continually recall the presence and universality of sin in man’s history:
What Revelation makes known to us is confirmed by our own experience. For when man looks into his own heart he finds that he is drawn towards what is wrong and sunk in many evils which cannot come from his good creator. Often refusing to acknowledge God as his source, man has also upset the relationship which should link him to his last end, and at the same time he has broken the right order that should reign within himself as well as between himself and other men and all creatures.
From the Catechism of the Catholic Church 397-401