The fact that Acts does not depend upon St. Paul's writings and nevertheless shows many undesigned points of contact with them, leads us to a very important conclusion. This conclusion is that the writer of Acts was a companion of St. Paul. It is incredible that a later writer, who took an eager interest in St. Paul's adventures, should have made no use of St. Paul's letters. Those letters made a deep impression upon St. Paul's contemporaries (cf. 2 Cor. x. 10), and they were carefully treasured by all succeeding generations. We can only explain the relation between Acts and the Pauline Epistles by the theory that the author of Acts was sufficiently intimate with the apostle to be able to write his book without feeling the necessity of enriching it by references to those Epistles. The theory, then, fits with the theory which is suggested to us by the "we sections." The only remaining question is whether this companion was, or was not, St. Luke. {107} He was evidently with St. Paul at Rome, and this makes it impossible to attribute the authorship of Acts to Titus, as there is no hint in the New Testament of Titus being there. Nor was the author Silas, for Silas was not with St. Paul on the third missionary journey, while the author of Acts was. Acts xx. 5, 6 seems to prove that the book was not written by Timothy. No one seems so likely to have been the author as St. Luke. For the writer of Acts xxvii. 1-xxviii. 16 evidently accompanied St. Paul to Rome, and we learn from Col. iv. 14 and Philem. 24 that St. Luke was with the apostle during his first imprisonment in that city. We may therefore say that every line of evidence points to the truth of the ancient tradition that St. Luke wrote Acts.