One alternative, purely natural explanation for the disciples’ claim to have seen Jesus after his death is grief-induced hallucinations. In these cases, a person misses his deceased loved one so much that he imagines that the person has come back from the dead to visit him. Maybe the disciples had similar hallucinations of the risen Jesus?
Besides this not explaining things like St. Paul seeing the risen Jesus, this explanation still doesn’t work for a variety of reasons.
Studies on grief-induced hallucinations show that true hallucinations are not common. The Hayes and Leudar 2016 study found only one case of grief-induced hallucination involving a non-family member of the deceased. Moreover, most of these cases involved only feeling the presence of a deceased person. Just 2 percent involved a tactile hallucination of touching the dead person, which would parallel the claims of having prolonged encounters with an embodied Jesus as described in Luke’s and John’s Gospels. Grief hallucinations also tend to persist for many years after death, but the claims that Jesus appeared to his disciples stop just a few weeks after his crucifixion.
In 2015, Gary Habermas and medical doctor Joseph Bergeron surveyed thousands of cases in the medical literature and could not find a single case of a group grief hallucination comparable to the group appearances described in the New Testament. One psychologist cited in their paper said,
I have surveyed the professional literature (peerreviewed [sic] journal articles and books) written by psychologists, psychiatrists, and other relevant healthcare professionals during the past two decades and have yet to find a single documented case of a group hallucination, that is, an event for which more than one person purportedly shared in a visual or other sensory perception where there was clearly no external referent.
Even some critics of the Resurrection admit that there are no other examples of a group hallucination the way it’s proposed to have happened to the apostles. Kris Komarnitsky in his book Doubting Jesus’ Resurrection writes,
If the group appearance traditions in 1 Corinthians 15:5-7 are the result of people simultaneously hallucinating Jesus, there is no comparable example anywhere in history that I am aware of.
Other skeptics, however, claim that there are analogous cases of group hallucinations, and these could explain what happened to Christ’s disciples. But when you look at the examples closely, you see that they are too different from the Resurrection to be an adequate explanation. Here are some examples skeptics offer:
Alien Abductions. Nearly all abduction stories can be explained as culturally conditioned, private hallucinations involving only one person . . . or they are outright hoaxes. People who report these encounters often receive positive attention, and they’ve only become more widespread after science fiction tales about aliens became popular in the 1950s and television shows began to report on alleged abduction stories. And as I said, they almost always happen to individuals at night, who awaken and suffer from “sleep paralysis.” In this condition, your mind has woken up, but you are unable to move your body. People in this condition often see things that aren’t real.
The handful of cases where multiple people say they were abducted by aliens are probably hoaxes or come from hypnotic suggestion. Most experts believe that Betty and Barney Hill, for example, suffered from sleep deprivation and misinterpreted an aircraft warning beacon as a UFO. More importantly, the particular aspects of the alien encounter were recovered under hypnosis three years later and bear a striking similarity to an episode from the sci-fi series The Outer Limits that aired two weeks before their hypnosis session.
Bigfoot Sightings. There are no cases of a group of people having an extended encounter with Bigfoot similar to what the Gospels portray the disciples having with Jesus. At best, these encounters involve a group of people misidentifying an animal in the woods or a hoaxer as Bigfoot. But the disciples intimately knew Jesus and would have been able to tell if the person they encountered was actually he. And if they really weren’t sure, they could check Christ’s empty tomb to dispel any doubt about who had appeared before them.
Mass Hysteria. This happens when a phenomenon transmits collective illusions of threats, whether real or imaginary, through a population and society as a result of rumors and fear. It also includes cases of seemingly infectious bizarre behavior, like medieval dancing outbreaks or the 1962 Tanzania laughing epidemic. But none of these cases involves a group of people all seeing the same impossible thing, like a dead man who came back to life.
Finally, one of the most common examples skeptics offer, at least to Protestant apologists, is Marian apparitions. Atheist biblical scholar Hector Avalos says Marian apparitions “form the closest parallel to the Jesus apparition stories. . . . Marian apparitions have been reportedly witnessed simultaneously by millions of people, but most evangelical apologists do not see that as proof that Mary is alive” (193). And atheist Richard Dawkins has said, “It is not easy to explain how 70,000 people could share the same hallucination” (91).
Although not all Marian apparitions are authentic, or they could be malevolent supernatural encounters, Catholics have no problem accepting that many of the cases skeptics cite, like the incident at Fatima in 1917, are legitimate miracles. Although Protestants might perform miracles that vindicate the power of the gospel (like healing someone in the name of Jesus), there seem to be many more cases in Catholicism of miracles whose message is not just a vindication of the gospel, but a vindication of distinctly Catholic doctrines, like the real presence of Jesus in the Eucharist being seen in hosts that turn into human flesh; relics that heal people; and Marian apparitions in which Mary says she is the Immaculate Conception, like the apparition at Lourdes. For a measured use of miracles to prove Catholicism, I recommend Tyler McNabb’s and Joseph Blado’s article “Mary and Fátima: A Modest C-Inductive Argument for Catholicism.”
So let’s pull all this together. Skeptics often try to explain groups of people seeing the risen Jesus as cases of group hallucinations, yet they can’t offer other similar examples of groups of people having a grief-induced hallucination. In fact, the closest examples they do offer are groups of people seeing the Virgin Mary after the end of her earthly life . . . which isn’t a problem for Catholic defenders of the Resurrection.