That said, I'm going to present one of the best arguments I've heard for the key belief of Christianity: the resurrection of Jesus. It's mostly from a sermon preached at my church, Hope Community Church, plus some of my own thoughts. My pastor started with a quote from the Handbook of Christian Apologetics:
We believe Christ’s resurrection can be proved with at least as much certainty as any universally believed and well-documented event in ancient history. To prove this, we do not need to presuppose anything controversial (e.g., that miracles happen). But the skeptic must also not presuppose anything (e.g., that they do not). We do not need to presuppose that the New Testament is infallible, or divinely inspired or even true. We do not need to presuppose that there really was an empty tomb or postresurrection appearances, as recorded. We need to presuppose only two things, both of which are hard data, empirical data, which no one denies: the existence of the New Testament texts as we have them, and the existence (but not necessarily the truth) of the Christian religion as we find it today.The basic assumption for the argument is that a man named Jesus really lived around the time the gospels say he did, he was a religious teacher who was crucified, and soon after this his followers began spreading his teachings saying he'd risen from the dead. Even secular historians from around that time who would have been all too eager to disprove Christianity admit to this much. The argument breaks the death and resurrection of Jesus into five possibilities:
1. Jesus did not die. He was resuscitated by the cool of the tomb.
The so-called 'swoon' theory. It asserts that Jesus in fact did not die on the cross and was merely unconscious when he was buried. A few days later, he came to, feeling much better, and walked out of the tomb, whereupon he began telling people he'd miraculously risen from the dead.
The key to these theories is to take them apart and examine them in detail. Consider what Jesus went through leading up to the crucifixion. He was arrested, starved, deprived of sleep, food, and drink, severely beaten, flogged (a treatment that killed some people right then), and, of course, crucified. If there was one thing Roman soldiers were good at, it was killing people. Crucifixion is one of the most horrific ways to die imaginable. Just to make sure Jesus was good and dead, they stabbed him with a spear for good measure. The swoon theory asserts that after all this, Jesus was somehow still alive, and after lying in a tomb with no food, water, or medical attention for 36 hours, suddenly felt 'much better', enough so to push aside the stone sealing his tomb shut, overpower the armed Roman guards, and go around telling people he'd been resurrected. After all that happened to him, he would have been an absolute mess, a far cry from the glorified "resurrection body" he was described as having. I doubt he would have convinced anyone he'd been miraculously resurrected. There's just no way he could have survived all that.
2. Jesus did die.
If this (much more likely possibility) is the case, there are four subpossibilities:
a. Jesus did not rise from the dead, but his disciples didn't know it.
The two most popular theories to explain this are that his disciples either went to the wrong tomb by mistake and, finding it empty, thought he'd been resurrected, or that they hallucinated.
Let's take these apart: if they went to the wrong tomb, all any of the Jews or Romans would have had to do to disprove Christianity (which they would have been eager to do) would have been to direct them to the right tomb. It's very hard to believe that during the entire rise of the early church, that no one noticed that the empty tomb the disciples found was the wrong one. (Also that everyone believed Jesus had been resurrected when no one actually saw him)
As for hallucinations: while it's certainly possible for someone to hallucinate meeting and conversing with an imaginary person, it's inconceivable for two (let alone five hundred) people to hallucinate the same person at the same time. Also, as with the other theory, all anyone would have had to do to shut the early Christians up would have been to actually procure Jesus' dead body and show it to everyone. Next theory.
b. Jesus did not rise from the dead, and his disciples knew it.
i.e. Christianity is the biggest hoax in human history. This was the theory the Jews at the time believed (Matthew 12:11-15); that the disciples stole Jesus' body and falsely proclaimed he'd been raised. My disproof of this one comes from human nature. Except for John and Judas, all of Jesus' disciples were martyred. It is much easier for me to believe Jesus did rise than to believe that anyone would live and die for something he knows to be a lie.
c. Jesus did not rise from the dead, and his disciples never said he did.
i.e. Christianity is a myth; Jesus is on the same level as Zeus. There is simply very little evidence for this theory. Nothing about the gospels is written in the "myth" style; it is presented as a series of historical events, with lots of tie-ins to the real world and real people. The gospels and epistles are very clear that Jesus really did rise from the dead, literally. The myth theory is a much more recent invention (from the last few centuries), while we have abundant evidence that Christians believed in a literal resurrection before that. And again, can you see a Greek myth-writer being martyred for his belief that Europa was abducted by Zeus in the form of a bull?
With all of these theories seeming pretty unlikely, we come by elimination to the last one:
d. Jesus did rise from the dead. Christianity is true. Hallelujah!