The 19th c. German scholar whose masterpiece, The Synoptic Gospels: Their Origin & Historical Character (1863), established scholarly consensus in favor of the Two Source hypothesis. Born in Karlsruhe as the son of a prominent theologian, Holtzmann became professor of NT at Heidelberg (1865-74) and then Strasbourg (1874-1904). He wrote extensive commentaries on the gospels & studies on other NT works. But his earlier work on the synoptic problem remains his major legacy.

In it Holtzmann argued that all three synoptics were based on a lost narrative of the reminiscences of Peter, which he called Ur-Markus ("Original Mark") or source A, which Matthew and Luke independently supplemented with sayings drawn from a logia collection (Source L). Two decades later, in summarizing his research in his Historico- Critical Introduction to the New Testament (Freiburg, 1885), he abandoned the Ur-Markus hypothesis, concluding that Matthew and Luke used canonical Mark.  This adjustment simplified Holtzmann's formulation of the two source hypothesis by making it necessary to postulate only one lost synoptic source, the logia collection that Johannes Weiss later called Q. This became the source theory that has been the basis of most critical research on the synoptic gospels ever since.     

Other On-line resources:

• Heinrich Julius Holtzmann - 1902 biographical tribute in The Open Court retracing Holtzmann's influence on modern biblical studies (digitally archived by Southern Illinois University Library).

• Holtzmann's Life of Jesus according to the 'A' Source - John Kloppenborg traces how Holtzmann's theory of Markan priority influenced 19th c. images of Jesus (archived by U of Toronto's Computing in the Humanities and Social Sciences).