The apostles and the early evangelists, as Westcott suggests, were preachers, not historians, not pamphleteers. They believed in living witnesses more than in transmitted documents. They did not write out the record at first, partly because they were naturally disinclined to write, and partly, no doubt, because they expected the immediate return of our Lord to earth. Their gospel was therefore for many years a spoken and not a written word. As they went on repeating it, changes would occur in the repetition of the words; to the remembrance of one and another of them the Spirit of truth would bring facts and circumstances that they did not think of at first; words, phrases, gestures of our Lord would reappear in the memory of each, and thus the narrative became varied and shaded with the personal peculiarities of the several writers. Years passed, and the expected return of the Lord to earth did not take place. The churches were spreading over Asia and Europe, and the apostles were unable personally to instruct those who were preaching the gospel in other lands. Thus the need of a written record began to make itself felt; and the apostles themselves wrote out the story which they had been telling, or it was written for them by their companions and fellow-helpers in the gospel. The oral gospel as it lived in their memories would form, no doubt, the substance of it, and the written memoranda of the discourses and incidents, to which Luke refers, would be drawn upon in completing the biography. The oral gospel thus carefully prepared and transmitted by memory would be substantially the same, yet many differences in arrangement of words and phrases would naturally have crept in; the written memoranda would in many cases be verbally identical. And each Evangelist, gleaning from this wide field, would collect some facts and sayings omitted by the others. There are other explanations of the origin of the Synoptic Gospels, some of which are ingenious and plausible, but I shall not burden your minds with them, since the theory which I have presented appears to me the simplest, the most natural, and the most comprehensive of them all.