In Christian doctrine, the fall of man, or simply the fall, was the transition of the first humans from a state of innocent obedience to God to a state of guilty disobedience to God. Though not named in the Bible, the concept for the Fall comes from Genesis chapter 3. Adam and Eve live at first with God in a paradise, but the serpent tempts them into eating the fruit from the tree of knowledge of good and evil, which God forbade. After doing so they become ashamed of their nakedness and God consequently expelled them from paradise. Many Christian denominations believe that the fall corrupted the entire natural world, including human nature, causing people to be born into original sin, a state from which they cannot attain eternal life without the gracious intervention of God. Protestants hold that Jesus gave his life as a sacrifice for the elect, so they may be redeemed from their sin, both actual and original. In other religions, such as Judaism, Islam, and Gnosticism, the term "the fall" is not recognised and varying interpretations of the Eden narrative are presented. The term "prelapsarian" refers to the sin-free state of humanity prior to the fall.
Original sin, also called ancestral sin, is, according to a Christian theological doctrine, humanity's state of sin resulting from the fall of man, stemming from Adam's rebellion in Eden. This condition has been characterized in many ways, ranging from something as insignificant as a slight deficiency, or a tendency toward sin yet without collective guilt, referred to as a "sin nature", to something as drastic as total depravity or automatic guilt of all humans through collective guilt.
The concept of original sin was first alluded to in the 2nd century by Irenaeus, Bishop of Lyons in his controversy (written in Greek) with certain dualist Gnostics. Its scriptural foundation is based on the New Testament teaching of Paul the Apostle ( and ), and . Tertullian, Cyprian, Ambrose and Ambrosiaster considered that mankind shares in Adam's sin, transmitted by human generation. Augustine's formulation of original sin was popular among Reformers, such as Martin Luther and John Calvin who equated original sin with concupiscence, affirming that it persisted even after baptism and completely destroyed freedom. Within Roman Catholicism, the Jansenist movement, which the Church then declared heretical, also maintained that original sin destroyed freedom of will.