There are three aspects to the debunking of the Resurrection:
1) The Gospels are not reliable sources of information; they are poor quality evidence
2) The claims of the Resurrection are incredible claims which require very good quality evidence
3) If the Christian claims of the Resurrection are not true, then what, if anything, actually took place, and what hypothesis can better explain the data?
Before I do this, it should be apparent from the previous posts in this series that almost any naturalistic explanation is, by analysis of probability, more probable than a supernaturalistic one.
Here is an explanation from Bart Ehrman:
Why was the tomb supposedly empty? I say supposedly because, frankly, I don’t know that it was. Our very first reference to Jesus’ tomb being empty is in the Gospel of Mark, written forty years later by someone living in a different country who had heard it was empty. How would he know?…Suppose…that Jesus was buried by Joseph of Arimathea…and then a couple of Jesus’ followers, not among the twelve, decided that night to move the body somewhere more appropriate…But a couple of Roman legionnaires are passing by, and catch these followers carrying the shrouded corpse through the streets. They suspect foul play and confront the followers, who pull their swords as the disciples did in Gethsemane. The soldiers, expert in swordplay, kill them on the spot. They now have three bodies, and no idea where the first one came from. Not knowing what to do with them, they commandeer a cart and take the corpses out to Gehenna, outside town, and dump them. Within three or four days the bodies have deteriorated beyond recognition. Jesus’ original tomb is empty, and no one seems to know why.
Is this scenario likely? Not at all. Am I proposing this is what really happened? Absolutely not. Is it more probable that something like this happened than that a miracle happened and Jesus left the tomb to ascend to heaven? Absolutely! From a purely historical point of view, a highly unlikely event is far more probable than a virtually impossible one…” [Jesus Interrupted, pp. 171-179]
In other words all sorts of fairly improbable scenarios are inevitably going to be more likely than an extremely improbable one.
What do I think happened? Well, I can only roughly hypothesise. I do think someone called Jesus was crucified. I think this does the best job of explaining the cult of Jesus which went on. I think he was an apocalyptic figure whose followers were expecting him to be some kind of Messiah. He was an itinerant preacher who went about charismatically attracting followers, spreading a socialistic and revolutionary message.
But he was killed, and his followers were not expecting this. As a result, they went though classic cognitive dissonance experiences. Some would have left, but most would have stayed on and post hoc rationalised such a problematic piece of evidence against their case. Leon Festinger first noted this phenomena in psychological terms when a UFO cult had a failed rapture day, and the world continued. fringe members left but committed members rationalised the disappointment to continue with stronger commitment.
If we double this up with what I have talked about in the previous post:
- Jesus was a disgraced blasphemer of sorts
- He was crucified and his body eaten by wild animals as was the norm
- He would have had a criminal’s burial in a shallow, unknown grave
- His followers would not know where he was buried
- This supports the fact that his tomb was not venerated as he did not have one, or it was unknown
- Stories developed out of this, and committed members had experiences which were later expanded or mythologised
A variation could be
- Jesus was left on the cross, but had to be removed before Passover sundown, and was hastily given a temporary tomb (there is precedence for this)
- Jesus was then later moved from the tomb, lent by someone (perhaps Joseph of Arimathea, perhaps someone else forgotten in time, with J of A mythologised over), and put in a shallow grave as per protocol
- The people or person who moved the body were unknown to the disciples
- The disciples came to the tomb where they thought Jesus was buried, only to find it empty
- Tales of angels were mythologised onto this account, or it even involved hallucinations (some 13% of people who have experienced the death of somone close orally or visually hallucinate)
I am not overly swayed by hallucinations, but only because I have not been around death and people who have lost others too much. One of my frinds used to hallucinate smells of her dead grandmother.
Here is a list of other potential theories:
- The authorities removed the body, for one reason or another, from the cross or tomb
- The women went to the wrong tomb
- The disciples stole the body to contrive a resurrection
- The tomb was never visited, and the whole set of events were mythologised
- Sometimes called the “swoon theory”, the idea that Jesus never actually died on the cross and was taken down alive
In order to save me doing the writing myself, here is a list compiled by the Iron Chariots Wiki to explain the data from a naturalistic perspective:
The evidence for the resurrection is open to a number of naturalistic explanations
“Swoon theory” refers to the hypothesis that Jesus didn’t really die on the cross, but rather was taken down alive and recovered in the tomb. It was made famous in the 19th century by Heinrich Paulus, as well as by fictional works that postulated an Essene conspiracy that assisted in the ruse. Today it has few advocates, though Richard Carrier recently published a partial defense of it.  Carrier argued that it was actually the least likely naturalistic explanation, but it still had a chance of occurring of 1 in 6,800. This is sufficient to rule out a miracle, because if every 1 in 6,800 event were declared miraculous, we would have to believe that royal flushes are miraculous.
A related but arguably distict theory is the “Autoresuscitation Theory”, invoking an unusual phenomenon of spontaneous, natural return from a state of clinical death accepted as a naturalistic occurrence in the medical literature, including a set of 32 cases compiled here: 
Assimilation of hearsay
Psychological research by Loftus and Palmer in 1974 demonstrates that testimony assimilates external information and cues without the person even realizing it. Psychological research carried out by Festinger and Carlsmith in 1959 shows that people can change their understanding when there is otherwise insufficient evidence to justify a conclusion that the subjects wish to come to. Both of these can lead to exaggerated or inaccurate narratives being given.
The effect studied by Festinger and Carlsmith also poses a fatal problem for David Strauss’s argument that the swoon theory fails to account for the amazement of the disciples.
Wars and fights don’t generally end suddenly for political reasons, as it would amount to an admission that it wasn’t right in the first place. Paul wanted something to say along with his ceasing to persecute Christians, giving him motivation to invent or modify a story as to what happened. Paul’s visions (even if they existed) are obvious embellishments, as he would have no way of knowing it was Jesus, as he didn’t even know what Jesus ‘s face looked like. We can see him saying many things that he clearly did not do any fact-checking on, and this must include the purported appearance of Jesus to a group of 500 people claimed by Paul. (Source: New Testament historian Bart Ehrman) This was combined with the above effects to result in exaggerated claims made later by others.
1908 psychological research by Yerkes and Dodson shows that high anxiety can impair judgement in non-trivial situations. Claims apologists make that a centurion pronouncing death or later recollection by early church members would be accurate under death threats can be turned on their head: Anxiety impairs, not enhances judgment, in such cases.
Twin and moved body
Jesus had an identical twin and the body was moved by someone (several possibilities here)
Twin and wrong tomb
Jesus had an identical twin and Mary Magdalene made a mistake while locating the tomb. Others may have been induced to make a mistake by the effect documented in the psychological research “Asch Conformity Experiments” (1950’s) although the Gospels are inconsistent on who exactly was and wasn’t there.
Minor details may have been corrupted. Even those who subscribe to the “minimal facts” approach must admit that some of the minor details are unreliable and inconsistent among the Gospels. This poses problems for those apologists trying to debunk some of the naturalistic explanations, as they often need to assume the truth of a minor detail. Example: claiming that the inability of Jesus to push away the stone according to “swoon theory” depends on an unreliable detail – namely, the weight of the stone.
Keith Parsons has recently argued that recent experience with people who believe themselves to have been abducted by aliens makes the hallucination hypothesis more plausible, and that many standard apologetic objections to the hypothesis would also require us to believe in alien abduction.
Biblical scholar Dale Allison has made a similar argument based on reports of apparitions of the dead. In particular, he notes “examples of collective hallucinations in which people claimed to see the same thing but, when closely interviewed, disagreed on the details, proving they were not, after all, seeing the same thing.”
Primary and Composite naturalistic explanations
The swoon and hallucination theories are “primary”, only invoking one part. By contrast, the “twin plus moved body” and “political correctness plus hearsay assimilation” are composite, requiring a “synthesis” of more than one part. Apologists essentially never mention these, or even the possibility of composite theories, because it would show that their case can have holes poked in it.
The standard objection to the fraud theory is that the disciples would not have died for a lie. However, documentation of their martyrdoms is weak. The earliest comes at the end of the 2nd century and is only for Peter and Paul. Also, it has been suggested that the disciples may have lied for what they believed was a higher cause.
The resurrection and Jesus mythicism
To some extent, the debate over the resurrection would be moot if it were demonstrated that Jesus never existed. However, some mythicists, notably Richard Carrier, accept that early Christians reported visions of Jesus, and these are explained as hallucinations.
Even assuming that a person named Jesus existed, there is no reason to believe that the Bible provides an accurate account of events in his life. The resurrection and the accompanying details may have been invented at a later date.
Generalized Littlewood’s Law
If we generalize Littlewood’s Law of Miracles to an approximately 1,000-month-long human lifespan, and to a total population of humans who have ever existed of 100,000,000,000 then to reject the null (no supernatural intervention in the natural world) hypothesis with 95% confidence we need, to avoid the so-called multiple testing fallacy , the probablity of all naturalistic explanations to be below
P = 5 * 10-22 or 1 in 2,000,000,000,000,000,000,000. The apologist has no case unless every single potential naturalistic explanation is truly astronomically improbable, not just seemingly unlikely.
Now, you can claim that some of these interpretations or theories or claims are inherently improbable. They may even be utterly wildly improbable. But that still puts them in the category of being far more probable, and with higher prior probability through precedence, than a dying and rising incarnate god-figure, who prays to himself and sacrifices himself to sit on his own right hand which somehow pays for the sins of humankind, which he created and had ultimate control over, for all of time. See my previous posts for more on these probabilities.
I know what I think is more probable.