What is a hallucination? It is a false perception of something that is not there. The question then is did Jesus’ followers perceive Jesus appeared to them, but he was not really there? Could Jesus’ disciples have been grieving after his crucifixion so much that they perceived he appeared to them, but he wasn’t really there? What we know about hallucinations today is that they are private and occur in the mind of an individual. Even if there was a group of people in the same frame of mind where they could hallucinate, each person would experience their own hallucination as an individual experience. Hallucinations cannot be experienced as a group, nor can they be shared.
It’s interesting how the Bible describes some of Jesus’ appearances as occurring in groups. Since the same hallucination cannot be seen by everyone in a group, this disqualifies those appearances as hallucinations. But how do we know that they all saw the same thing? Couldn’t they all have said they saw Jesus and yet seen and heard different things at while all hallucinating at the same time? Does the Bible describe what they saw when Jesus appeared to them?
Although each appearance documented in the Bible describes each having occurred at different locations, included different messages, had different audiences, and were different experiences with Jesus, there is no evidence to suggest that while gathered as a group, everyone saw and heard different things. The Bible records one reality at each experience. We don’t have something that says something like: while Jesus appeared to the disciples, Peter saw and heard one thing, while John saw and heard something else, and so forth. The message is clear, the disciples together witnessed and heard the same thing at each separate appearance of Jesus they experienced together.
An even larger group is mentioned by Paul in his first letter to the Corinthian church (1 Corinthians 15:1-19), which includes one of the oldest and most important creeds that the early church formed dated 55 A.D.:
"Now I make known to you, brothers and sisters, the gospel which I preached to you, which you also received, in which you also stand, by which you also are saved, if you hold firmly to the word which I preached to you, unless you believed in vain.
For I handed down to you as of first importance what I also received, that Christ died for our sins according to the Scriptures, and that He was buried, and that He was raised on the third day according to the Scriptures, and that He appeared to Cephas, then to the twelve. After that He appeared to more than five hundred brothers and sisters at one time, most of whom remain until now, but some have fallen asleep; then He appeared to James, then to all the apostles; and last of all, as to one untimely born, He appeared to me also. For I am the least of the apostles, and not fit to be called an apostle, because I persecuted the church of God. But by the grace of God I am what I am, and His grace toward me did not prove vain; but I labored even more than all of them, yet not I, but the grace of God with me. Whether then it was I or they, so we preach and so you believed.
Now if Christ is preached, that He has been raised from the dead, how do some among you say that there is no resurrection of the dead? But if there is no resurrection of the dead, then not even Christ has been raised; and if Christ has not been raised, then our preaching is in vain, your faith also is in vain. Moreover, we are even found to be false witnesses of God, because we testified against God that He raised Christ, whom He did not raise, if in fact the dead are not raised. For if the dead are not raised, then not even Christ has been raised; and if Christ has not been raised, your faith is worthless; you are still in your sins. Then also those who have fallen asleep in Christ have perished. If we have hoped in Christ only in this life, we are of all people most to be pitied."
But didn’t Paul, formerly known as Saul, experience a different type of appearance by Jesus described in Acts 9:3-7? “As he neared Damascus on his journey, suddenly a light from heaven flashed around him. He fell to the ground and heard a voice say to him, “Saul, Saul, why do you persecute me?” “Who are you, Lord?” Saul asked. “I am Jesus, whom you are persecuting,” he replied. “Now get up and go into the city, and you will be told what you must do.” The men traveling with Saul stood there speechless; they heard the sound but did not see anyone.” Here again we read that Saul wasn’t alone during this appearance, and that although the other men did not see what he did, they heard the sound. Since they heard what Saul heard, it is no longer an individual experience that qualifies Jesus’ appearance to him as merely a hallucination."
Another thing to consider is that Paul and James, Jesus’ brother who also experienced an appearance from Jesus, were both devoted Jews and skeptics of Jesus. Upon their separate appearance experiences, they became leaders of the early Church. Paul, in particular, had no reason to mourn the crucifixion of Jesus, as he was on his way to persecute Christians. It doesn’t seem reasonable to think that these skeptics were in a frame of mind to hallucinate an appearance of Jesus. Being devoted Jews, believing Jesus to be the Messiah would go against their religion, and have eternal implications for them.
What then did Jesus’ followers see in these appearances which led them to say they saw Jesus? Doesn’t the Bible mention that at first some of them did not recognize him? Wouldn’t they be able to instantly recognize Jesus after having seen him for years? The Bible seems to teach us that Jesus’ resurrected body was different from his prior earthly body. Although it doesn’t tell us why they couldn’t recognize him at first, it does say that eventually they did recognize him. Jesus’ followers held to their eyewitness testimony of having seen Jesus appear to them in word and in deed.
Consider now what you have more support for believing: that Jesus’ appearances were simply hallucinations or that they were proof that the reason the grave was empty was because Jesus did resurrect. If you believe they were simply hallucinations, you will still need to account for Jesus’ empty tomb. (Source used for this article: "The Case For The Resurrection Of Jesus" by Gary Habermas and Michael Licona. Find it here: https://amzn.to/2MQ7zLE )