The author of the Acts expressly states that he wrote “the first treatise (ton prōton logon) concerning all things, O Theophilus, that Jesus began both to do and to teach until which day he gave command through the Holy Spirit to the apostles whom he had chosen and was received up” (Act 1:1.). There is no room for dispute that the reference is directly to the Gospel according to Luke as we have it now. Like the Gospel the book is dedicated to Theophilus. And, what is even more important, the same style appears in both Gospel and Acts. This fact Harnack has shown with great pains and conclusiveness. There is the same interest in medical matters and even Cadbury, who denies by implication the Lukan authorship, admits identity of authorship for both books.

There are some scholars who are willing to admit the Lukan authorship of the “we” sections when the author uses “we” and “us” as in chapter 16:10-40; 20:6-28:31. It has been argued that Luke wrote a travel-document or diary for these sections, but that this material was used by the editor or redactor of the whole book. But, unfortunately for that view, the very same style appears in the Acts as a whole and in the Gospel also as Harnack has proven. The man who said “we” and “us” in the “we” sections wrote “I” in Act 1:1 and refers to the Gospel as his work. The effort to disprove the unity of the Acts has failed. It stands as the work of the same author as a whole and the same author who wrote the Gospel.

Beyond a doubt Luke employed a variety of sources for this great history as he did for the Gospel (Luk 1:1-4). In fact, Cadbury argues that this Prologue was meant to apply to the Acts also as Volume II whether he intended to write a third volume or not. Certainly we are entitled to say that Luke used the same historical method for Acts. Some of these sources are easy to see. Luke had his own personal experience for the “we” sections. Then he had the benefit of Paul’s own notes or suggestions for all that portion where Paul figures from chapter 8 to chapter 28, since Luke was apparently with Paul in Rome when he finished the Book. This would include Paul’s sermons and addresses which Luke gives unless one wishes to say, as some do, that Luke followed the style of Thucydides and composed the kind of addresses that he thought Paul would make. I see no evidence of that for each address differs from the others and suits precisely the occasion when it was delivered. The ancients frequently employed shorthand and Paul may have preserved notes of his addresses. Prof. C. C. Torrey, of Yale University, argues in his Composition and Date of Acts (1916) that Luke used an Aramaic document for the first fifteen chapters of the Acts. There is an Aramaic element in certain portions of these chapters, but nothing like so pronounced as in Luke 1 and 2 after Luk 1:1-4. It cannot be said that Torrey has made out his case for such a single document. Luke may have had several such documents besides access to others familiar with the early days of the work in Jerusalem. There was Simon Peter whom Paul visited for two weeks in Jerusalem (Gal 1:18) besides other points of contact with him in Jerusalem and Antioch (Acts 15 and Galatians 2). There was also Barnabas who was early Paul’s friend (Act 9:27) and who knew the beginnings as few did (Act 4:36.). Besides many others it is to be observed that Paul with Luke made a special visit to Caesarea where he spent a week with the gifted Philip and his daughters with the gift of prophecy (Act 21:8.). But with all the inevitable variety of sources for the information needed to cover the wide field of the Book of Acts the same mind has manifestly worked through it and it is the same style all through that appears in the “we” sections where the writer is confessedly a companion of Paul. No other companion of Paul carries this claim for the authorship and no other was a physician and no author has the external evidence from early writers.

There are three views about the date of the Acts. Baur and his Tubingen School held the second century to be the date of this late pamphlet as they termed it after the fashion of the Clementine Homilies. But that view is now practically abandoned save by the few who still strangely oppose the Lukan authorship. Probably the majority of those who accept the Lukan authorship place it in the latter part of the first century for two reasons. One is that the Gospel according to Luke is dated by them after the destruction of Jerusalem because of the prophecy by Jesus of the encompassing of the city by armies. Predictive prophecy that would be and so it is considered a prophecy post eventum. The other reason is the alleged use of the Antiquities of Josephus by Luke. Josephus finished this work a.d. 93 so that, if Luke did use it, he must have written the Acts after that date. Usually this argument is made to show that Luke could not have written it at all, but some hold that he may have lived to an age that would allow it. But it cannot be assumed that Luke used Josephus because of his mention of Theudas and Judas the Galilean. They differ so widely (Act 5:36. and Josephus, Ant. XX. v, 1, 2) that Von Dobschutz (Dictionary of the Apostolic Church, art. Josephus) argues that the two accounts are entirely independent of each other. So Luke (Luk 13:1.) alludes to a Galilean revolt not mentioned by Josephus and Josephus records three revolts under Pilate not referred to by Luke. A comparison of the accounts of the death of Agrippa I in Act 12:20-23 and Ant. XIX. viii, 2 redounds to the credit of Luke. The Josephus phase of the argument may be brushed to one side. The third view, held by Harnack and adopted here, is that Luke wrote the Acts while with Paul in Rome and finished the book before Paul’s release, that is by a.d. 63. This is the obvious and natural way to take the language of Luke at the close of Acts. Events had gone no farther and so he ends the narrative right there. It is argued against this that Luke contemplated a third volume and for this reason closed with the arrival of Paul in Rome. But the use of prōton (first) in Act 1:1 is a common Koiné[28928]š idiom and does not imply three volumes any more than first and second stories with us means that the house has three. Of course this date for the Acts puts the date of the Gospel further back either in Caesarea (57 to 59) or in Rome (60 to 62). And that means that Mark’s Gospel is still earlier since Luke used it for his Gospel and the Logia (Q) earlier still. But all these dates are probable in the light of all the known facts.

A special problem arises concerning the text of Acts inasmuch as the Codex Bezae (D) with some other Western support presents a great many additions to the Neutral-Alexandrian text of Aleph A B C. Blass has even proposed the idea that Luke himself issued two editions of the book, an attractive hypothesis that is not generally accepted. J. M. Wilson has published The Acts of the Apostles from Codex Bezae. The whole subject is elaborately treated by J. H. Ropes in Vol. III, The Text of Acts in Part I of The Beginnings of Christianity. Besides thorough discussion of all the problems of text involved Ropes gives the text of the Vatican Codex (B) on the left page and that of Codex Bezae (D) on the right, making comparison easy. Blass’s ideas appear in his Acta Apostolorum.