Change in personality:
On the night Jesus was betrayed one of the apostles was betraying him and another was denying he knew him. They then went to their homes, hiding behind locked doors for fear of the Jewish (1) authorities who did not believe in Jesus (John 20:19), and then returned to their old professions (John 21:2ff.). Months later they were meeting openly where people in the street could hear them speaking (Acts 2:1ff., nb. Acts 2:6), speaking publicly before the crowd (Acts 2:14) and seeing thousands of people join with them (Acts 2:41). They were highly postive, energised and totally changed people (cf. Acts 2:42-47 with John 20:19). After this they healed people in Jesus' name (Acts 3:4-8) and rejoiced in facing persecution on account of his name (Acts 5:40f.), and went forth to the farthest corners of the Roman Empire and beyond to India and the barbarian tribes to preach about Jesus and his rising from the dead in the face of persecution unto death.
Something had happened to these people to completely change their perspective.
Number of wittnesses:
Paul states there are over 500 wittnesses to Jesus' resurrection from the dead (I Cor.13:3-8), not including women who were not counted as wittnesses under Roman law. At the time he writes this most of these are still alive (I Cor.13:6), so although we can't walk up to one of these people and verify what Paul was saying, those who received his letter could. These wittnesses saw Jesus after his resurrection on several occasions, under several different circumstances, in several different places and times (over 40 days, Acts 1:3) as several different groups (eg. Matthew 28:9; 16f., Mark 16:9; 12; 14, Luke 24:15; 36, John 20:14; 19; 26, 21:1ff., Acts 1:3-9).
Later these people would be heavily persecuted and many would die for claiming Jesus had risen from the dead.
Dying to prove a fake:
So we're looking at well over 500 people including the women who claimed Jesus had risen from the dead and that they had seen it. Given the variety of people, circumstances and groupings during which these appearences occurred, the suggestions of mass hallucination (something extremely rare anyway) or hypnosis seem nonsensical to me.
Given the familiarity with death people of these times had and the fact that several of them were there when Jesus died on the cross and saw the Roman soldiers checking to see if he was alive (John 19:25-35), the suggestion that Jesus had merely fainted and would come to 3 days later and move a stone weighing several tons out of the way, cause the soldiers to run away even though a Roman soldier faced death for losing a prisoner (cf. Acts 12:19), then appear to over 500 people over 40 days and convince them all that he had risen from the dead to the point where they would die rather than deny that he had, also seems nonsensical to me.
If I wasn't a Christian who has the Holy Spirit and communes with Jesus on a daily basis as well as having other reasons for believing Jesus is stilll alive today, I would probably think that the number of wittnesses and the variety of circumstances over which they saw him and the fact that they would die claiming he had risen from the dead was pretty compelling evidence. As it is I know that's what occurred through my own experience.
Notes:
- (1): use of the term 'Jews' in the gospel of John:
John uses the term to refer to those Jewish authorities who opposed Jesus. Jesus and all his apostles including John were Jewish, as were all the early church and the apostle Paul who was a pharisee (Phil.3:4f.). Several of the Jewish authorities had sympathies with Jesus such as Nicodemus (John 3, 7:50, 19:38f.) and many joined the church early on (Acts 15:5).