There are several categories of objections to the Christian religion. Such disputes can be from non-Christians about Christian doctrine that is generally accepted by most Christians or it can be between Christians. There are objections on theological grounds. These dispute claims Christians make about the nature of God, what is required for salvation, the consequences of not being saved, how to interpret the Bible, and a whole host of doctrinal issues. There are objections based on philosophy meaning what is good and evil, are morals absolute or relative, what gives meaning to our lives, what is existence and why, and so on. And then there are objections to claims Christians make about Jesus, specifically his ministry, death, and resurrection. These latter arguments, more than the others, place upon Christians a burden of proof because, rather than being about general principles, they are about historical events.
Atheists in particular argue that Christianity has the burden of proof to back up its claims and so they need to be convinced. Any Christian should be able to respond to this. It isn’t just about faith and never has been. The primary source of proof for Christianity are the Gospel stories as well as St. Paul’s letters which attest to the Passion account. You can doubt all of Christ’s ministry from the Virgin birth up to his arrest, but, if you believe that Christ died and was raised to new life, you have accepted the Gospel or at least made that first step. St. Paul literally says so in one of his letters (1 Cor. 15) that Christ’s physical resurrection is the fact upon which the Christian hope stands or falls.
That Jesus lived in the 1st century and was crucified under Pontius Pilate is not disputed by any reputable historian, atheist or otherwise. So the main burden is on the resurrection. (Oxford professor N.T. Wright wrote a 700 page book answering this question but here is an article sized version of his argument.)
We cannot reach back and understand what occurred historically then. All we have are the Gospel accounts, all of which were written to Christian communities, and St. Paul. The primary argument in favor of the resurrection is to look at what happened to the church and think about it in 1st century Jewish terms. In other words, what was likely to happen given the society at the time? There had been before Jesus and after him several purported Messiah figures, revolutionaries, and self-proclaimed prophets. He is the only one who continued to be the Messiah after his execution.
Crucifixion was in both Greco-Roman and Jewish culture an extremely shameful death, certainly not one fit for a Messiah. Jesus’ movement should have scattered after that happened. It should have found another Messiah as had happened when Jesus was a child with Judas the Galilean. Instead, it grew and flourished, unified in the belief that Jesus had been raised from the dead and that they (his original followers) had seen him.
If this didn’t actually happen, then one is forced to argue that either they made it up to keep the movement going or they were tricked or tricked others. Steeped in 2000 years of Christian tradition, we might see the former as a plausible move, but, culturally, this didn’t fit with 2nd temple Judaism at all. It required a complete change in worldview. And, just as physical phenomena require some logical explanation, psychological and sociological phenomena do as well. If his disciples stole his body out of the tomb and claimed to have seen him, they would have had to have had a good reason for doing so, and this is without knowing that they were about to create a world spanning religion.
Did Jesus, perhaps, instruct them to do this because this was how he interpreted scripture? That seems unlikely. Jesus believed he would be raised. To instruct his disciples to make it appear as if he were raised would have exposed him as a charlatan to them. This would be a pretty big conspiracy, not simply the miraculous claims of one or two men.
Was it their own idea because Jesus taught that this would happen and when it did not they decided to conspire to make it look like it had? This seems to be the story that the Jewish authorities told (Mat. 28:13). If they did so, then they would have had to conspire thereafter (until their deaths) that this had actually happened. Was this some sort of mutual oath that they took together after his crucifixion? Then the question would be why? What was in it for them if none of it were true and they knew it? All the disciples appear to have met violent ends at the hands of the authorities while living out the church’s mission and risking harm both by travel and from Jewish and Greco-Roman authorities. Now, maybe until the killing and arrests started, they might have been alright living a lie, but it seems unlikely that they would continue to risk persecution and death knowing that their whole new movement was fraudulent, and they were persecuted from day one. Jesus made sure of that by claiming to be the Son of God and the Messiah. They weren’t leading a genuine violent revolution. They didn’t hope to gain a kingdom on Earth from it. They were gaining some money and property for communal use but, if you accept what was written in the book of Acts, the church in Jerusalem was deeply impoverished. It was a movement by and for the poor that attracted only a few wealthy and powerful Jews. The rewards don’t fit with the risks. There was nothing in it for them if it was all a lie.
The second option could be true. (This is called the “swoon” theory.) Maybe Jesus was a trickster who escaped the cross somehow and pretended to be raised. Assuming Jesus was actually crucified, this is not at all plausible. The Romans were extremely efficient at killing people. If Jesus had been crucified, he would have died, no question. His injuries from scourging alone could have been fatal. Swapping identities with someone else seems possible if someone were willing to be crucified in his place (seemingly unlikely given that his disciples were rather cowardly). Also, Judas Iscariot would have to have been in on it since he is the one who identified Jesus to the authorities. Could he have identified someone else? Some of his disciples were present at Jesus’ questioning and at the crucifixion and would have known it was not him. Were they in on it too? Now we get to the same issue as in the conspiracy theory where Jesus dies. There is no way that Jesus could have pulled this off without a lot of people knowing about it. Given that the rewards of the Christian life at that time were spiritual, not material, and the risks were very much material in terms of life and property, there is no clear motivation.
(Many Muslims believe that Jesus miraculously swapped faces with someone else which means that God pulled off a different miracle than the one Christians claim occurred. This would require that either the resurrection didn’t happen at all [same conspiracy issues] or that Jesus for some reason chose to lie and say he was raised when he didn’t. If we accept that Jesus is a prophet, then it’s hard to explain a lie that, for Muslims, is blasphemous. The argument falls apart.)
A third option is that later Christians modified the story that the original disciples told. In other words, there was no resurrection account at all and this was added later by St. Paul and his followers, who didn’t know Jesus before his crucifixion, and the Gospel writers simply accepted Paul’s message verbatim. We know that, for example, Gnostics heavily modified the message of the original Gospel accounts to support a very different Gospel, so this is perhaps plausible.
There are a few problems with this narrative. Suppose the original disciples never claimed they saw him after his death. (Perhaps somebody else stole Jesus’s body and they claimed he was raised but all the resurrection accounts are later additions.) Rather, suppose they claimed he was raised and immediately taken. We know that St. Paul claims that they saw him. Moreover, we know that St. Paul knew the original apostles and met with them in Jerusalem as well as elsewhere and that they were aware of what Paul was preaching. Still, perhaps they were somehow unaware of that small detail he was preaching. (This is unlikely because he had traveling companions at all times who would have given him away.)
The question is: Why did they start the church? St. Paul didn’t start the church. He came along later and many churches, including the church in Rome to whom he was writing in Romans, were started by others. Although Paul founded several churches and his letters were highly prized, he was basically an itinerant preacher, not the leader of the movement at all. That job fell to James, Jesus’ brother, and it was James who sent Paul out to preach to the Gentiles.
People at that time didn’t believe that people got raised from the dead and given new bodies. Resurrection was actually a very vague concept about something that would happen at the end of time. They would not have concluded, upon finding his body missing, that he had been raised. All the Gospel accounts make it clear that this was unexpected.
Even if you don’t believe those, you have to provide a logical reason why they would conclude he was raised from the dead. Did Jesus just tell them before his crucifixion that his missing body meant he was raised and the Gospel and Paul’s descriptions of their seeing him were merely embellishments on this teaching?
If so, this embellishment appeared within the apostles’ lifetimes, which seems implausible. Far more plausible for embellishments to appear after their lifetimes. This is precisely why the Gospel accounts and letters of Paul are so important because they were written during living memory of Jesus’ ministry. Although they contain their own embellishments, such as the nativity stories which differ significantly between Matthew and Luke, the Passion account appears to have been nailed down almost immediately and the broad details of what happened are clear. Some one would have had to have originated the embellishment early on, during the apostolic age, and it seems like this would have had to have come from the original apostles.
If someone like Paul were preaching a different message, he would have been shot down unless he could make a convincing case. Paul did so with circumcision and contention on that issue continued for decades after his death. He could hardly have invented the resurrection account and made a case to the very people to whom it was supposed to have happened.
Another interesting and perhaps stronger point was that the first witnesses to the risen Jesus differ in Paul’s account versus the Gospel accounts. He says that Jesus appeared to “Cephas [Peter], then to the twelve. Then he appeared to more than five hundred of the brothers and sisters at one time, most of whom are still alive … Then he appeared to James, then to all the apostles.” (1 Cor 15:5-7) If the resurrection embellishments came from Paul, that seems unlikely as he would have been the source, and they would have wanted to agree with them. Instead, all the Gospels say women were the first witnesses, a fact that Paul completely ignores, and nobody would have added in as an embellishment since women were not considered trustworthy witnesses at that time in either the Jewish or Greco-Roman world. It would have been a ridiculous fact to make up. It would be far more plausible for Paul’s account to be made up, which, in fact, it is to some extent since it ignores the actual first witnesses. This makes an even stronger case that the resurrection sightings came not from Paul but from the original apostles, starting with Jesus’s female followers.
These are all the main objections to the resurrection. Most other ideas can be reduced to similar implausible conspiracies that make little psychological or sociological sense. It is of course impossible to make an iron clad argument. We cannot perform repeated experiments to determine if the resurrection actually happened as we can with science. This is not the science of the repeatable but the science of historical inquiry using incomplete data. Still, to accept the resurrection, we do have to keep an open mind about what is possible. If we automatically assume that people do not rise from the dead, we cannot even follow arguments in favor of the resurrection. We have already convinced ourselves before we even start. People in the 1st century also did not believe people rose from the dead, so they had the same difficulties we do. Their lack of advanced, modern scientific understanding of biology didn’t change that. They were not more credulous about such things than we are. They had to be convinced in the same way we do: that with God all things are possible.