Original sin, in Western Christian theology, the sin of Adam, by which all humankind fell from divine grace. Saint Augustine was the fundamental theologian in the formulation of this doctrine, which states that the essentially graceless nature of humanity requires redemption to save it. The purpose of baptism is to wash away original sin and to restore the individual to an innocent state, although even after baptism a tendency to sin remains as a result of original sin.

Orthodox Theology--We learn from this starting point that Adam was like a child, fully capable of growing up in obedience to his Heavenly Father. . . . Like a child he had to be taught. But like many children and adults he would not be taught. He wanted to be autonomous; to be God-like without God and he thereby brought death down upon his head. Listen to St. Irenaeus: "Man was a little one, and his discretion still undeveloped, wherefore also he was easily misled by the deceiver."

St. Irenaeus and the Fathers generally, therefore, do not see death as a divine punishment for the disobedience of our first parents. This distortion arose later in the west under the influence of Augustine. . . . The expulsion of Adam and Eve from Paradise and the angel standing guard with the flaming sword is not an act of divine retribution but a compassionate and merciful provision lest we eat of the second tree, the Tree of Life, and die eternally. The fruit of this tree, if we had eaten it, would have condemned us forever.