From the Cathechism of the Catholic Church:
The "tree of the knowledge of good and evil" symbolically evokes the insurmountable limits that man, being a creature, must freely recognize and respect with trust. Man is dependent on his Creator, and subject to the laws of creation and to the moral norms that govern the use of freedom.
Man's first sin
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. Constituted 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...
A hard battle
The doctrine of original sin, closely connected with that of redemption by Christ, provides lucid discernment of man's situation and activity in the world. By our first parents' sin, the devil has acquired a certain domination over man, even though man remains free. Original sin entails "captivity under the power of him who thenceforth had the power of death, that is, the devil". Ignorance of the fact that man has a wounded nature inclined to evil gives rise to serious errors in the areas of education, politics, social action and morals.
The consequences of original sin and of all men's personal sins put the world as a whole in the sinful condition aptly described in St. John's expression, "the sin of the world". This expression can also refer to the negative influence exerted on people by communal situations and social structures that are the fruit of men's sins.
This dramatic situation of "the whole world [which] is in the power of the evil one" makes man's life a battle:
The whole of man's history has been the story of dour combat with the powers of evil, stretching, so our Lord tells us, from the very dawn of history until the last day. Finding himself in the midst of the battlefield man has to struggle to do what is right, and it is at great cost to himself, and aided by God's grace, that he succeeds in achieving his own inner integrity...
After his fall, man was not abandoned by God. On the contrary, God calls him and in a mysterious way heralds the coming victory over evil and his restoration from his fall. This passage in Genesis is called the
Protoevangelium ("first gospel"): the first announcement of the Messiah and Redeemer, of a battle between the serpent and the Woman, and of the final victory of a descendant of hers.
The Christian tradition sees in this passage an announcement of the "New Adam" who, because he "became obedient unto death, even death on a cross", makes amends superabundantly for the disobedience, of Adam. Furthermore many Fathers and Doctors of the Church have seen the woman announced in the
Protoevangelium as Mary, the mother of Christ, the "new Eve".