It is customary to observe that the defeat of Marcionite Christianity underscored the intimate relationship between the church and Judaism. It meant that Christians would continue to hear readings from the OT and thus be led to understand the story of ancient Israel as part of their own history. It meant that they would be able to see Jesus as part of an ongoing history and as a participant in an ancient and vibrant Jewish culture. This judgment is certainly correct, but the proto-orthodox victory also had the potential to bring Jews and Christians into conflict over the interpretation of these texts. If Christians believe that the same God who sent Jesus Christ also sent Moses, they must develop some ways to address the apparent differences between their teachings. The Gospel of Matthew contributed to a resolution of this problem by having Jesus use six antitheses: “You have heard …but I say to you” (see Matt 5: 21-48). However one interprets the contents of these antitheses, the form suggests that the words of Jesus are to be substituted for those of Moses. It is also essential that the OT prophets bear witness to Jesus. In contrast to Marcion’s Gospel, the canonical version of Luke has the resurrected Jesus explain to two of his disciples how the Scriptures, including Moses and all the prophets, spoke of a suffering Messiah and thus predicted the coming of Jesus (Luke 24:26-27). In Acts 3:18, Peter makes essentially the same observation.
While I appreciate the fact that Tyson concludes that Marcion wasn't anti-Jewish, this understanding of the antitheses in Matthew is - well - stupid (I'm sorry, but because I am not a professional scholar I don't feel obliged to mince my words). The decisive point is that Clement in Stromata clearly understands all the heretics - even the Marcionites by implication - had this reading in their gospel and more specifically understood Paul to have had access to this material.
The manner in which Clement specifically develops the argument that 'thou shalt not lust' is at least part of the Ten Commandments demonstrates that they understood Matthew 5:21, 22; 27, 28 as 'antithetical' in a specifically antinomian sense. In other words, Clement argues that 'thou shalt not' lust appears in both the gospel and the Law therefore there is compatibility between the two revelations. Yet the heretics - including the Marcionites - must have argued in the exact opposite direction. Indeed Clement's argument is in fact very weak. There is a difference between saying 'don't lust after your neighbor's wife' (something your wife might say after your honeymoon) and 'don't lust' at all (something your wife might say if you've been married for ten years or more).
Indeed what has escaped Tyson is the variant reading which appears in the Diatessaron and which we just noted was common to the Marcionites, Clement of Alexandria, Origen, the Origenists and most importantly Ephrem and the Syrian Diatessaronic tradition. Here there is a real 'antithesis' between the Law and the gospel because the specific reading 'do not lust' at all is coupled with a second 'antithesis' - the Law says do not murder but I say 'do not be angry.' The implication moreover is that the Christian god (a) does not lust and (b) is never angry - something which clearly distinguishes him from the passionate Jewish Lord.
