Context: John's Gospel does not conform to the other three Gospels in many respects and for this reason some have doubted its historical accuracy, believing it to be a symbolic work for doctrinal and devotional purposes rather than a record of events. Others believe, however, that one of John's purposes was to record episodes in the ministry of Christ which are not included in the first three Gospels. It is true that he provides more commentary and interpretation than the others do. The authorship of this Gospel is uncertain; but scholarly opinion is that the writer, if not John the Apostle, is one John the Elder–who had apparently some close personal connection with him. If John's testimony is added to that of the other Gospels, it becomes likely that Jesus made numerous trips to Jerusalem during the period of His ministry, which may have lasted three years. These trips were made at times of festival, when the city was crowded and He could preach to large audiences; and His arguments with the Pharisees in the Temple were frequent enough for them to consider Him a real threat to the religio-political establishment of the time. This fear would have been reinforced by the ease with which He confounded their arguments and turned their accusations of lawbreaking against them, the unanswerable refutations of their arguments, and the large crowds which gathered to hear Him. If it is accepted that John's testimony is largely supplementary, then the Pharisees' fanatical determination to kill Jesus becomes more plausible. John describes one of these episodes in Chapter 5; Jesus heals a helpless invalid, infuriating the Pharisees. He later delivers an inspired sermon which effectively confounds all their accusations. John's description of the invalid and his cure carries an unusually strong effect of realism and immediacy, as though he had seen it occur: