Paul gives a list of those who supposedly saw a resurrected Jesus. The list includes "the twelve," a reference to the twelve apostles. Isn't this a reliable witness to the claim that Jesus rose from the dead?
Paul claims that Jesus was seen, soon after his alleged resurrection, by "the twelve" (1 Corinthians 15:5). The term, "the twelve," refers to the inner-circle of Jesus' closest disciples. The respective later versions of the alleged post resurrection encounter between Jesus and his innermost circle of disciples found in the Gospels and the Book of Acts are careful to record that due to Judas' defection there were only eleven disciples at that time.
Matthew alleges that "the eleven disciples went to Galilee, to the mountain which Jesus designated. And when they saw him, they worshipped; but doubted" (Matthew 28:17); Mark maintains that "afterward he appeared to the eleven themselves as they were reclining" (Mark 16:14); Luke states that "they arose that very hour and returned to Jerusalem, and found gathered together the eleven and those who were with them" (Luke 24:33). John, alone, does not give a precise number for those disciples left after Judas' defection but does refer to "Thomas, one of the twelve" (John 20:24). Here "the twelve" simply indicates that Thomas was one of the original twelve. Acts 1:13 lists eleven disciples to which was added Matthias in order to make up the full quorum (Acts 1:26). It is seen from Acts 1:12-26 that Matthias was not appointed to be a member of the apostolic inner-circle until sometime after their alleged group encounter with a resurrected Jesus. Whether referred to as "the twelve" or as the deficient "the eleven" they are a cohesive group separate from those who were with them. However, the term "the twelve" apparently did not become institutionalized, so that when deficient of that number the group did not bare that name.
Paul does not mention either the defection of Judas or the appointment of Matthias. He does refer to the inner-circle of "the twelve" experiencing a post resurrection appearance at a time when the Gospels and Acts respectively maintained there were only eleven. There is no reason to believe that Paul institutionalized the term "the twelve" and was actually referring to "the eleven." In addition, it is possible that Paul never heard of any defection by Judas or his replacement by Matthias because these incidents never happened. They may be legends developed within the church during the interval between Paul's writing to the Corinthians and the authorship of the Gospels and Acts. As it stands, Paul's use of the term "the twelve" to describe a postresurrection appearance to the inner-circle disciples cannot be considered trustworthy. At a time when the inner-circle of disciples precisely numbered eleven to call them "the twelve" places in doubt, either the reliability of Paul's sources concerning the disciples or the story of Judas' defection.