It is often said that the truth of Christianity can be “proved” by the devotion of the many people who have died rather than deny Christ. The problem with this assertion is that willingness to die for a belief is no proof of the beliefs validity. There are surely many people who have died for causes of dubious truth.
What’s more, one could easily and truthfully argue that nearly anyone might be convinced to die for a cause given the right indoctrination. The many Christian Martyrs may be sincere but sincerity is not enough to make one correct.
I believe the actual strength of this argument in regards to Christianity may be the number of eye-witnesses who gave their lives. In particular the Apostles each have well documented (as much as something of near antiquity can be well documented – your requirements may vary from mine) martyrdoms.
Unlike a non-eyewitness, the eyewitness has real physical reasons to believe or disbelieve. We often place our emphasis on the Apostles belief. It may be better to think for a moment the possibility of unbelief. If Christ did not rise from the grave, the Apostles would have clearly known this. Perhaps they carried on and fabricated evidence in a desire to further their leaders work. This would have perhaps worked until faced with death for what you personally knew was a lie. It may even be possible that the rare, hyper-devoted person would die for this lie. However with Christianity we have multiple eye-witnesses giving their lives for “the lie”. I think the odds start to get much lower that this would happen.
Critics often remind Christians of the other “Messiah cults” of the time. I see these not as a stumbling block but further proof that false movements tend to die out because the eye witnesses are given reason to doubt and do exactly that. They doubt and give up. As noted, it might be possible for someone heavily invested in a lie to die for it but to have multiple people do so is not as likely. If the Christian “movement” was a lie, I believe the odds would be that most of the eye-witnesses would find a way to safely walk away when persecution flared up.
Christianity is unique in that multiple first-hand witnesses end up dying for their belief. One may argue that later Christians gave their lives after periods of prolonged exposure to Church propaganda. Later Christian martyrs believe because they were never presented with any physical evidence to the contrary of their belief. The same cannot be said of the Apostles. If Christ did not rise, they would have known it. This knowledge would make it very hard to die for something you personally know is not true.
Other faiths do not have a large number of “founding Martyrs”. Even among those that do, their strong faith is in that of an “ideal”. A belief in the truth of teachings. Early Christian martyr’s died in defense not of a ideal or beautifully stated holy work. Early Christian martyr’s died for refusing to deny a nearly absurd claim – the claim that Jesus Christ died and then rose back to life.
Given the right motivation a person could choose to die for all sorts of noble causes. The Christian Apostles died for a claim that they each would have had first hand knowledge of – did Christ rise from the dead? Many may be able to die for an ideal or indoctrinated belief. How many would die for a fact which they knew to be false?