The papers which follow were first delivered at the second Durham-Tubingen Research Symposium on Earliest Christianity and Judaism, which met at the University of Durham in September 1989. The first symposium had met the previous year in Tubingen and focused on an earlier stage of the relationship between earliest Christianity and Judaism, "Paulus, Missionar und Theologe, und das antike Judentum", the papers of which have already been published in the same series1. The first symposium commemorated the 50th anniversary of the great Tubingen theologian, Adolf Schlatter, 1852-19382. It was equally fitting that the second should honour the memory of one of the greatest scholars of earliest Christian texts, the Bishop of Durham, Joseph Barber Lightfoot, 1828-89, meeting as it did on the centenary of his death. It is particularly appropriate that the spirit of Lightfoot should have presided over a joint Durham-Tubingen research symposium and on the subject of why and when earliest Christianity became something different from the Judaism of the same period. For Lightfoot's scholarly work had been very largely dominated by his ongoing debate with F. C. Baur and the Tubingen school3. And the main theme of their debate was very close to the theme of the 1989 symposium. Baur indeed had defined "the ultimate, most important point of the primitive history of Christianity" precisely as the issue of