St. Augustine did not “invent” original sin, as some allege. Adam and Eve invented it in the Garden of Eden, and as a result all men are born in the state of original sin.
The Catechism of the Catholic Church explains, “Revelation gives us the certainty of faith that the whole of human history is marked by the original fault freely committed by our first parents” (CCC 390). This reality is demonstrated clearly in these passages of Scripture.
“And the Lord God commanded the man, saying, ‘You may freely eat of every tree of the garden; but of the tree of the knowledge of good and evil you shall not eat, for in the day that you eat of it you shall die.'” (Gen. 2:16-17)
“[The Lord said] ‘Have you eaten of the tree of which I commanded you not to eat?’ The man said, ‘The woman whom thou gavest to be with me, she gave me fruit of the tree, and I ate.’ Then the Lord God said to the woman, ‘What is this that you have done?’ The woman said, ‘The serpent beguiled me, and I ate.’ . . . To the woman he said, ‘I will greatly multiply your pain in childbearing; in pain you shall bring forth children, yet your desire shall be for your husband, and he shall rule over you.’ And to Adam he said, ‘Because you have listened to the voice of your wife, and have eaten of the tree of which I commanded you, “You shall not eat of it,” cursed is the ground because of you; in toil you shall eat of it all the days of your life; thorns and thistles it shall bring forth to you; and you shall eat the plants of the field. In the sweat of your face you shall eat bread till you return to the ground, for out of it you were taken; you are dust, and to dust you shall return.'” (Gen. 3:11-19)
“Therefore as sin came into the world through one man and death through sin, and so death spread to all men because all men sinned . . . Yet death reigned from Adam to Moses, even over those whose sins were not like the transgression of Adam, who was a type of the one who was to come. But the free gift is not like the trespass. For if many died through one man’s trespass, much more have the grace of God and the free gift in the grace of that one man Jesus Christ abounded for many. And the free gift is not like the effect of that one man’s sin. For the judgment following one trespass brought condemnation, but the free gift following many trespasses brings justification. If, because of one man’s trespass, death reigned through that one man, much more will those who receive the abundance of grace and the free gift of righteousness reign in life through the one man Jesus Christ. Then as one man’s trespass led to condemnation for all men, so one man’s act of righteousness leads to acquittal and life for all men. For as by one man’s disobedience many were made sinners, so by one man’s obedience many will be made righteous.” (Rom. 5:12-19)
“But in fact Christ has been raised from the dead, the first fruits of those who have fallen asleep. For as by a man came death, by a man has come also the resurrection of the dead. For as in Adam all die, so also in Christ shall all be made alive. But each in his own order: Christ the firstfruits, then at his coming those who belong to Christ.” (1 Cor. 15:21-23)
“And you he made alive, when you were dead through the trespasses and sins in which you once walked, following the course of this world, following the prince of the power of the air, the spirit that is now at work in the sons of disobedience. Among these we all once lived in the passions of our flesh, following the desires of body and mind.” (Eph. 2:1-3)