<P> Original sin, also called ancestral sin, is a Christian belief of the state of sin in which humanity exists since the fall of man, stemming from Adam and Eve's rebellion in Eden, namely the sin of disobedience in consuming the forbidden fruit from the tree of the knowledge of good and evil . 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 . </P> <P> The concept of original sin was first alluded to in the 2nd century by Irenaeus, Bishop of Lyon in his controversy with certain dualist Gnostics . Other church fathers such as Augustine also developed the doctrine, seeing it as based on the New Testament teaching of Paul the Apostle (Romans 5: 12--21 and 1 Corinthians 15: 21 - 22) and the Old Testament verse of Psalms 51: 5 . Tertullian, Cyprian, Ambrose and Ambrosiaster considered that humanity shares in Adam's sin, transmitted by human generation . Augustine's formulation of original sin was popular among Protestant reformers, such as Martin Luther and John Calvin, who equated original sin with concupiscence (or "hurtful desire"), affirming that it persisted even after baptism and completely destroyed freedom, although Augustine said that free will was weakened but not destroyed by original sin . The Jansenist movement, which the Catholic Church declared to be heretical, also maintained that original sin destroyed freedom of will . Instead the Catholic Church declares "Baptism, by imparting the life of Christ's grace, erases original sin and turns a man back towards God, but the consequences for nature, weakened and inclined to evil, persist in man and summon him to spiritual battle ." "Weakened and diminished by Adam's fall, free will is yet not destroyed in the race ." </P>

What was the original sin in the bible