Essentially, Original sin is the doctrine, shared in one form or another by most Christian churches, that the sin of Adam and Eve in the Garden of Eden changed or damaged human nature, such that all human beings since the fall are innately predisposed to sin, and are powerless to overcome this predisposition without divine intervention. There are wide-ranging disagreements among Christian groups as to the exact understanding of this doctrine, and some Christian groups deny it altogether.

Original sin in the Old Testament

According to the account in Genesis 3, the original humans lived in a state of intimate fellowship with God, and enjoyed a perfect harmony with one another and with nature. They were, however, forbidden by God to eat of the fruit of "the tree of the knowledge of good and evil." The serpent (identified in Christian tradition with Satan) persuaded Adam and Eve to disobey this commandment. This led to several dire consequences, including the loss of intimate fellowship with God, man's susceptibility to physical death, a distortion of the relationship between the man and the woman, a predisposition to sin, and the loss of man's harmonious relationship with nature. All these consequences were 'inherited' by Adam and Eve's descendents.

Original sin in The New Testament

The New Testament teaching on original sin is briefly summarized by the Apostle Paul, who wrote: "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." (Rom 5:12 NRSV).

The experience of original sin, and the spiritual pain it produces in the one who wishes to please God, is dramatically summed up by Paul in the following verses: "I do not understand my own actions. For I do not do what I want, but I do the very thing I hate. Now if I do what I do not want, I agree that the law is good. So then it is no longer I that do it, but sin which dwells within me. For I know that nothing good dwells within me, that is, in my flesh. I can will what is right, but I cannot do it. For I do not do the good I want, but the evil I do not want is what I do. Now if I do what I do not want, it is no longer I that do it, but sin which dwells within me. So I find it to be a law that when I want to do right, evil lies close at hand. For I delight in the law of God, in my inmost self, but I see in my members another law at war with the law of my mind and making me captive to the law of sin which dwells in my members. Wretched man that I am! Who will deliver me from this body of death?" (Romans 7:15-24)

The solution to this dilemma is stated by Paul in these terms: "For God has done what the law, weakened by the flesh, could not do: sending his own Son in the likeness of sinful flesh and for sin, he condemned sin in the flesh, in order that the just requirement of the law might be fulfilled in us, who walk not according to the flesh but according to the Spirit." (Romans 8:3-4)

Though the New Testament doctrine of original sin is most clearly expressed by Paul, it is also implicit in the teachings of Jesus: for example in such words as: "And Jesus said to him, "Why do you call me good? No one is good but God alone." (Mark 10:18) and "I am the vine, you are the branches. He who abides in me, and I in him, he it is that bears much fruit, for apart from me you can do nothing." (John 15:5)

Original Sin in Catholicism

Original Sin as understood by Orthodox Christianity

Original Sin as understood by various Protestant denominations

Original Sin as understood by the Unification Church

Genesis 2:17 is a key Bible verse for discussions about the fall of man.

But of the tree of the knowledge of good and evil, thou shalt not eat of it: for in the day that thou eatest thereof thou shalt surely die. (KJV)

According to Unification Theology, Adam and Eve sinned by having a sexual relationship before they had reached perfection. The "fruit of knowledge" was a symbol of Eve's sexual love, which could be either good (if centered on God) or evil (if not). Eve was initially tempted into sin by the Archangel Lucifer, who seduced her. The reason Adam and Eve hid their "lower parts" after the Original Sin is similar to the reason a child having swiped cookies might hide their hands ("I have concealed by transgressions like Adam, by hiding my iniquity in my bosom." -- Job 31:33)