Presumption based on internal evidence is in favor of that theory. There has been no serious question as to the authorship of Matthew. Mark is supposed to have derived his knowledge of the events he recorded from Peter. Our knowledge of Peter's character leads us to believe that if he undertook to write a Gospel it would be such an one as the Gospel according to Mark. Such an expression as that in Mark 14:72, "When he thought thereon he wept," implies an intimate knowledge of him such as would be writ ten by Peter himself, or by a close associate. The introduction to Luke's Gospel shows that many Gospels were in existence when Luke wrote, and as he knew of them, he may have availed himself of the material they contained. His remark about writing "in order" suggests compilation. The authorship of the fourth Gospel has been hotly disputed, chiefly because some critics held that the writer of Revelation could not have written the elegant and cultured Greek of the Gospel, The majority of the commentators now, however, are in favor of the belief that John wrote it.
