Why do atheistic evolutionists conclude that Christianity is false? Basically, there rely on the following argument.
The Atheistic Evolutionist Argument
1) If evolution is true, there was no first, historical Adam.
2) If there was no first, historical Adam, there was no Fall.
3) If there was no Fall, the sinful condition of humanity is not an inescapable condition.
4) If the sinful condition is not an inescapable condition, moral and religious categories like ‘sin’ and ‘salvation’ are irrelevant or unnecessary, as evolution will take whatever course it takes by chance].
5) If salvation is irrelevant or unnecessary, there is no need for a Savior.
6) The heart or fundamental claim of Christianity is that it is necessary for Jesus to come as the Savior of the human race
Conclusion: If evolution is true [i.e. there was no historical Adam], then based on (5) and (6), Christianity is false.
The Theistic Evolutionist’s Blocking Strategy
The theistic evolutionist may try to block the atheistic evolutionist’s conclusion by arguing that even though we cannot solve the mystery of the origin of evil (however defined in evolutionary language), nevertheless, it is an undeniable empirical observation that ALL humans are born in ‘sin’. The need for a Savior remains.
Unfortunately, for the theistic evolutionist – If God uses the evolutionary process to create what appears to be a ‘sinful’ world, the absence of a Fall would suggest that God himself is solely responsible for the sinful condition of this world.
This disturbing conclusion should sober up many ‘progressive’ Christians who adopt theistic evolution along with the denial of a historical Fall of Adam, as any doubt about the goodness of God is fatal to the truth claim of Christianity.
For this reason, evangelical Christians insist on the doctrine of the historical and historic Fall of Adam as it preserves the insight that sin is an act of human free will, with the consequence of death to the human race. Sin is both universal (the sinful condition of humanity) and personal (it is my sin). The Fall is the reason why it is necessary for a sinless, Second Adam to save the world through his death and resurrection.
As the Westminster Confession of Faith teaches:
God has given man a will, which by nature is free, i.e. it is not forced or necessarily inclined toward good or evil.
In his state of innocence man had complete freedom and the natural ability to will and to do what is good and pleasing to God. God also made man so that he could lose that freedom.
Man fell into a state of sin by his disobedience and so completely lost his ability to will any spiritual good involving salvation. (WCF 9.1-3)
Covenant with Man
By his fall, man himself is incapable of life under that covenant , so the Lord made a second, the covenant of grace. In it he freely offers sinners life and salvation through Jesus Christ. (WCF 7.3)