The common thread in the arguments against the Christian faith is the philosophy of naturalism. Naturalism is an a priori belief that nothing exists apart from the natural, physical universe. Despite the inability of natural explanations concerning the beginning of the universe, the beginning of life, and the beginning of Christianity, no other explanations are allowed. Any metaphysical explanation is religion.
Yikes! Run for cover!
Antony Flew, the British philosopher and former leading spokesman for atheism, in his last book, Why There is a God, says that at the start of his career he made a promise to follow the evidence wherever it led.
The overwhelming evidence of design in the universe led him to abandon his naturalism in favor of theism.
Christians are often accused of being narrow minded, and I have known some who were. But in rejecting out of hand any metaphysical explanations on the grounds that they are religious, skeptics are manifestly narrow minded. There is a blind faith in this attitude that unnecessarily limits the search for truth.
The consensus view of scholars of antiquity is that Jesus Christ is a real historical person who lived in the first century in Israel. They agree that He spoke in the place of God, and that He was crucified. They nearly all agree that He was buried in a tomb and that the tomb was found empty after three days. Finally, they agree that the disciples really believed that God raised him from the dead. But then some abandon the obvious conclusion because of their commitment to naturalism.
Their problem is that any naturalistic explanation fails to explain the history to which they have already agreed. Over the centuries, every natural explanation has been discredited in scholarly circles.
The idea that Christianity began as a conspiracy of the disciples who borrowed from earlier pagan religions would never be offered as an explanation in the Academy. The conspiracy theory was destroyed first by Eusebius of Caesarea in 314 A.D. and again by William Paley in 1794. His book was required reading at Cambridge University until the twentieth century.
Today the conspiracy theory is only used at the popular level, through media such as the Zeitgeist movie and the Dan Brown novels, because that is the only place it can get a hearing. Still, natural explanations are being offered in the Academy. One scholar offered the idea that Jesus must have had a twin brother! Gerd Ludeman, an atheist German Bible scholar, contends that all of the disciples had a hallucination of the risen Christ.