Traces of a knowledge of the Acts are found in the Apostolic Fathers, in Justin, and in Tatian, and before the end of the second century the book occupied a place in the Canon undisputed except by heretics, such as the Marcionites, Manicheans, &c. The Muratorian Fragment and Irenæus (III. 14) are the first to mention Luke as the author of the Acts, but from that time on tradition has been unanimous in ascribing it to him. The only exception occurs in the case of Photius (ad Amphil. Quæst. 123, ed. Migne), who states that the work was ascribed by some to Clement, by others to Barnabas, and by others to Luke; but it is probable as Weiss remarks that Photius, in this case, confuses the Acts with the Epistle to the Hebrews. As to the date of its composition. Irenæus (III. 1. 1) seems (one cannot speak with certainty, as some have done) to put it after the death of Peter and Paul, and therefore, necessarily, the Acts still later. The Muratorian Fragment implies that the work was written at least after the death of Peter. Later, however, the tradition arose that the work was written during the lifetime of Paul (so Jerome, de vir. ill. 7), and this has been the prevailing opinion among conservative scholars ever since, although many put the composition between the death of Paul and the destruction of Jerusalem; while some (e.g. Weiss) put it after the destruction of Jerusalem, though still assigning it to Luke. The opposite school of critics deny Luke’s authorship, throwing the book into the latter part of the first century (Scholten, Hilgenfeld, &c.), or into the times of Trajan and Hadrian (e.g. Volkmar, Keim, Hausrath, &c.). The Tübingen School saw in the Acts a “tendency-writing,” in which the history was intentionally perverted. This theory finds few supporters at present, even among the most extreme critics, all of whom, however, consider the book a source of the second rank, containing much that is legendary and distorted and irreconcilable with Paul’s Epistles, which are looked upon as the only reliable source. The question turns upon the relation of the author of the “we” sections to the editor of the whole. Conservative scholars agree with universal tradition in identifying them (though this is not necessary in order to maintain the historical accuracy of the work), while the opposite school denies the identity, considering the “we” sections authentic historical accounts from the pen of a companion of Paul, which were afterward incorporated into a larger work by one who was not a pupil of Paul. The identity of the author of the third Gospel and of the Acts is now admitted by all parties. See the various Commentaries and New Testament Introductions; and upon the sources of the Acts, compare especially Weizsäcker’s Apost. Zeitalter, p. 182 sqq., and Weiss’ Einleitung, p. 569 sq.