Conditional Immortality is the doctrine that man was not given immortality as an eternal possession in the creation. When he fell, man lost his right to go on living, and God will take his life from him in an ultimate, complete and final sense in the Day of Judgment. The only way that man can obtain immortality, by this doctrine, is through accepting Jesus Christ and undergoing the new birth.
This is in contrast to the mostly-held view that man was given immortality at creation and that the human soul will never cease to exist. The Orthodox Fathers were divided on this doctrine and it cannot therefore be called Orthodox in any settled sense.
St. Augustine, while never making his own position very clear, claimed that the Bible does not teach the immortality of the mortal soul and that it first made its appearance as a doctrine in the rationalistic theology of Plato in the Myth of Er. Iranaeus, in Against Heresies, (4.38.3; 5.23.1), argued that man is free but still mortal. He must come to God through Jesus Christ-thus establishing obedience-in order to be immortal. Disobedience brings death. The Bible everywhere warns that the soul that sins shall die. So said Iranaeus.
Contrary to modern evangelical thought, this view has been very popular with fundamental theologians through the years. Some of the l9th-century American theologians who held it are CF Hudson, WR Hunington, CC Baker, LW Bacon and Horace Bushnell. Central to this as a biblical argument is the belief that God was preventing man from choosing immortality in his sinful state when He drove man out of the Garden, away from the Tree of Life, so that he would not eat of it and live forever in his sins. So sobering and terrible was this issue that God ordered man's execution if he tried to go back to the Tree of Life. This is thought to prove that man did not yet have immortality and God would not let him choose it, once he had fallen into corruption. If man had already been immortal, there would have been no point in keeping him from the Tree of Life. Man had one choice in this regard-the Tree of Life or the Tree of the Knowledge of Good and Evil, with its promise of death. Man chose the Tree of the Knowledge of Good and Evil. Had he chosen the Tree of Life first, man would have frozen himself in the eternal condition of finiteness and creature. He would never have known what it was like to be born of God, bone of His bone and flesh of His flesh. This is not to the credit of man's free choice, but to the glory of God's sovereignty and omniscience.
Those who believe that God gave man immortality in the creation and that he will go on existing forever say that this was simply a discipline by God. He would not allow man the privilege of eternal life, once he had sinned. Though the teachings of the Bible would seem to be clear enough on the issues of sin, death, corruption and judgment on the one hand and righteousness, eternal life and immortality on the other, this is an argument that will never be resolved on this earth to the satisfaction of everyone. But it is resolved in the counsels of God before the world was created.