Marcionism is a Christian heresy that was first denounced in 144 AD (CE). Marcion of Sinope proclaimed that the Old Testament could not be reconciled with the New Testament, and that the New Testament proclaimed a different god to the Old Testament. The God of the Old Testament was a malevolent God of law and materialist concerns (“Demiurg”); the God of the New Testament was a benevolent God of love and spiritual concerns. Marcion held that the first consequence of this insight needed to be the discarding of the Old Testament as authoritative (or even inspirational) in the Church. Only a carefully edited New Testament that is cleaned of any Jewish thought and is polemical towards Judaism would do.
Marcion developed those ideas early. He seems to have been excommunicated from the Church in Sinope by his own father due to his beliefs. After unsuccessfully attempting to spread his brand of Christianity in Asia Minor, Marcion joined the Church in Rome. It was probably here that he wrote down his argument and edited a new “Bible”. He was sure he could win over the Roman Church. In a full assembly Marcion argued with the presbyters of the Roman Church. The presbyters decided that what Marcion proclaimed was an aberration of the Christian message, a harmful heresy and a complete misunderstanding of the Gospel. Marcion was excommunicated and the large donations he had made to the Church were returned. Marcionism was therefore one of the first theologies declared to be a heresy, and probably the first we know of in the Church in Rome.
That was not the end of it. Marcion did find some followers and Marcionism spread throughout the Christian Church, with separate congregations that openly proclaimed their affiliation. In the West this clear identification with Marcion subsided before Christianity became the preferred religion of the Roman Empire under Constantine. In Syria, Marcionism as a distinct tradition existed longer, with some bishops of the official church investing effort in converting the heretics.
Nevertheless, even though few people and theologies across the millenia have described themselves as Marcionite, there always has been a strong tendency towards Marcionism in the Christian Church. Ever since the Church gained a strong following outside its Jewish roots, there has been a temptation not only to sever the link to those roots, but also to define the faith in distinction with Judaism and the Old Testament. During the Middle Ages that temptation was not as strong, because the Church at large did not engage closely with the Biblical text and the Old Testament was interpreted allegorically. With the Reformation in the 16th century and a closer reading of the Bible such a temptation grew. After all, if we regard the Bible as authoritative, some of what it has to say gets quite uncomfortable. It is far easier to press God and Jesus into our own image, to make them conform to the ideas of our times, if we disregard the historical reality and the strong claims of the Bible. Particularly from the 19th century onwards, when Theology tended towards a Philosophy of Religion, voices have arisen that have called the Church to discard the Old Testament. Some of these voices have been taken up more recently.
Since working in the Anglican Church in New Zealand I have been surprised by the strong Marcionism there. Here the most common expression is by using the Old Testament as the negative background to Jesus. The Old Testament is seen as a document of exclusion, narrow-mindedness and legalism; Jesus is portrayed in contrast with that as inclusive, open-minded and flexible. Little attention is given to the Old Testament except for showing how radical Jesus was. Jesus is then identified with the own cause and others who think differently are labelled as legalistic and pharisaic.
Of course, much of the New Testament can be understood better if we have an idea of the Old Testament background. And yes, differences need to be highlighted. But the relationship between the Old and New Testaments does not have to be seen mainly as one of contrast, but rather of continuity. With such an understanding we’ll probably get a lot further and closer to Jesus than seeing a constant conflict.
There is no denying that there is argument in the New Testament (and there is also in the Old Testament), but rather than an argument against the Scriptures, we see Jesus again and again arguing for the right interpretation of the Scriptures. Jesus does not argue that the Old Testament is “legalistic” or “out-dated”, or “irrelevant”; he does argue that it has not been applied faithfully, or that the interpretation of Jesus’ opponents does not realise that this not a time as usual, but the time of the fulfillment of God’s promises. Jesus did have a very real sense of the urgency of his mission and that this was a very particular time of God’s action with God’s people. That’s why fasting was not appropriate now, when the bridegroom was here, even though it is otherwise a good discipline.
So we should not see Jesus as reacting against the Old Testament, but rather as continuing and fulfilling it. Otherwise we fall into a new Marcionism. Just as Marcionism throughout the centuries, this new Marcionism is a distortion of the Gospel to make it conform more closely to current ideologies. Maybe the best way to guard against it is by reading and preaching both the Old and New Testaments and highlighting the continuity between them.