The testimony to the existence of our third Gospel, although it is not so old as that for Matthew and Mark, is still very early. It was used by Marcion, who based upon it his own mutilated gospel, and is quoted very frequently by Justin Martyr. The Gospel is first distinctly ascribed to Luke by Irenæus (III. 1. 1) and by the Muratorian Fragment. From that time on tradition was unanimous both as to its authorship and its authority. The common opinion—still defended by the great majority of conservative critics—has always been that the third Gospel was written before the destruction of Jerusalem. The radical critics of the present century, however, bring its composition down to a latter date—ranging all the way from 70 to 140 (the latter is Baur’s date, which is now universally recognized as very wild). Many conservative critics put its composition after the destruction of Jerusalem on account of the peculiar form of its eschatological discourses—e.g. Weiss, who puts it between 70 and 80 (while putting Matthew and Mark before the destruction of Jerusalem). The traditional and still prevalent opinion is that Luke’s Gospel was written later than those of Matthew and Mark. See the various commentaries and New Testament Introductions, and for a clear exhibition of the synoptical problem in general, see Schaff’s Ch. Hist. I. p. 607 sqq. On Luke in particular, p. 648 sqq.