The Gospel of St. Luke and the Acts of the Apostles are, we may say, universally admitted to be by the same writer. The reference of the Acts to the Gospel, the unity of style and tone of thought, all demonstrate them to be the production of one mind. Any circumstance therefore which proves the early existence of the Gospel equally proves the existence of the Acts of the Apostles. Now we have proof positive that the Gospel of St. Luke occupied an authoritative position and was counted an apostolic and sacred writing at Rome in the early years of the second century, say between 100 and 150, because when Marcion, whom we might call a primitive Antinomian, wished to compile a gospel suited to his own purposes, he took St. Luke's Gospel, cut out whatever displeased him, and published the remainder as the true version. The perversion and mutilation of St. Luke's work shows that it must already have held a high position in the Church at Rome, or else there would have been no object in mutilating it. Marcion's treatment of St. Luke proves the use and position the Gospel and the Acts must have occupied in days when the converts and companions of the Apostles were still alive.[15] That is as far as we can go back by external testimony. But then we must remember what these facts involve--that the Gospel and the Acts occupied authoritative positions in various parts of the world, and specially in Rome, Gaul, Africa, and Asia Minor, in the generation next after the Apostles. Then let us take up the Book of Acts itself, and what does this book, known at Rome and throughout the Christian world at that early period, tell us? It informs us that it was the work of the writer of the Gospel, and that the writer was a companion of the Apostle Paul throughout the portion of his career sketched in the latter part of the book. The Christian Church has never pinned its faith to the Lukian authorship of either the Gospel or the Acts. The question of the authorship of these books is an open one, like that of the Epistle to the Hebrews. The Acts has been attributed to Silas, to Timothy, to Titus; but I may say, without going into any further details on this question, that every attempt to ascribe the Acts to any one else save to the beloved physician has failed, and must fail, because he was the real author, well known to the living tradition of the Church of Rome in the early part of the second century, as that tradition is handed down to us in the language of the Muratorian Fragment. [15] See Dr. Sanday's _The Gospels in the Second Century_, and Dr. Salmon's _Introd. N.T._, pp. 204-208.