The doctrine of original sin is basically an attempt to explain the origin of evil and suffering.
In the early church, it can be accurately said there were two main views about the fall; one, that Adam and Eve either symbolised human nature in its entirety, or were two historical individuals.
Various church fathers speculated in various ways about the fall and what exactly happened. The Eastern Fathers tended to see the fall as a bad choice, a mistake made due to ignorance and neglect by Adam and Eve or by other beings in contemplating or abiding in the true Good, which was God. Western Fathers tended to see sin more as a transgression of divine law.
The divergence occured with St Augustine, who is the archetype for theology in the West and whose ideas have had immense influence. St Augustine believed that Adam and Eve were created as perfect and fully complete beings. They were given a choice; to obey or disobey God’s law in Eden. They freely chose to disobey God’s law, and were thus justly punished by God by death, corruption, suffering, and toil. Also in Augustine’s view the fall meant fallen humanity could not justly claim to the vision of God; in fact, God’s justice and the guilt of humankind demanded that God punishes all of fallen humanity to perdition. But by God’s mercy and grace he chooses and saves some human beings through predestination and grace, while allowing the rest to perish. Augustine also believed that sin had a hereditary nature, that is, each human being inherits the guilt from the original sin of Adam as well as the guilt from personal sins committed in life. The consequences of this (which are basically damnation) can only be removed by baptism.
The Eastern Fathers on the other hand, tended to see death and corruption as the main consequences of the fall, as God had originally made man and woman to undergo theosis, that is, to be divinised and blessed and taken into God’s glory, in this life and the next. Sin represented a free choice to miss this glory and a choice instead for nothingness and non-being from the fullness and life of God’s being. Sin then is both an inherited and mysterious form of corruption which infects the spirit/somatic whole of man in a strange way which seizes and takes hold of him, especially through the ‘passions’, which are disordered forms of affections for created things over God. Sin then is a form of physical, spiritual and psychological disease which corrupts and ruins man at the deepest levels but which can still be healed through grace and the sacraments. Through the grace of baptism and the sacraments and ascesis the Christian can still hope for theosis in this life, which is an anticipation of the glory the saints will have in the next.
Both Eastern and Western Christianity agree that sin exists, though in the West it is seen more in terms of violating God’s justice and law, while in the East it is missing the natural end humanity was made for, which is divinisation and the vision of God.