Last in the series of challenges for boundary definition of the early Christian community is the work that orthodox Christianity had to perform to define itself in relation to its various, heretical offshoots. Particularly, orthodox Christians faced a significant struggle with heretical groups over the problem of the old and the new, which includes, but is not limited to, the problem of the relationships between the Old and New Testaments. This issue grew especially large in the 2nd and 3rd centuries, and it encompassed problems of sociology (the relationship between Israel and the church), Christology (Jesus’ messiahship), theology (Jesus’ divinity), and eschatology (understanding prophesies of Israel’s scripture in light of Jesus). Moreover, the church had to sort through tensions along canonical-hermeneutical lines by defining how the Old Testament constituted specifically Christian scripture and how Jesus should affect one’s interpretation of it.
The New Testament resolves the problem of the old and the new by placing Christ as the climactic culmination of the old. In Christ, there are both continuity and genuine newness. At first glance, the Old and New Testaments are in some kind of tension, but the early church saw this tension as being resolved in Christ. The New Testament’s gaze is centripetal, looking to Christ in the center of its interpretive framework. For the New Testament writers, Jesus shows that the Old Testament must be understood as part of a story that transcends (even within history) the Old Testament’s own hopes. This position of the church was unstable and hard to defend in the patristic period. In the church’s attempts to stand firm on this unstable ground, many people wrongly tried to resolve the problem of the old and the new. For instance, some people denied the newness of the new in a reactionary mode like Pseudo-Clement, who collapsed the new back into the old by saying that: (1) Jesus is essentially the messiah only of the Jews, according to Jewish expectation, and (2) Christians should live under the law, excepting a few specific commandments. Alternatively, other people emphasized the newness of the new so that it lost its continuity with the old and effectively became foundationless (e.g., Marcion).
Baur said heresy often preceded orthodoxy so as to make the definition for orthodoxy very vague. Yet, as one examines this picture of early Christianity, a definition for orthodoxy or an orthodox reading of the Old Testament is possible as that segment of Christian thought and practice in the patristic period, which continued wrestling with the problem between the old and new. Orthodoxy refused to take a simple solution to the problem of the old and the new by denying or overly emphasizing the newness of the new.