I see a lot of people nowadays saying that the Old Testament is invalid, so I'm wondering if that is more of a modernist thinking or something that was said in the past before? If that was said in the past by people, how common was it for folk to say that?
Although I suspect you are thinking more of earlier theological arguments, this might be of knterest. It discusses how the Nazis dealt with the Jewish roots of Christianity.
Actually, the religious leader who came up with the first list of books considered canonical for the New Testament (not quite the same as what ultimately became standardized as the New Testament canon) was one of these. Marcion, a Greek shipbuilder.
For condemnations of Marcion's rejection of the Old Testament by contemporary, Against Marcion by Tertullian (who later found himself in a different heresy) is probably the most famous example.
Yes. There was an entire movement called of “structural supersessionism” or “replacement theology”. They said the god of the New Testament was so different from the god of the Old Testament they couldn’t be the same person, and besides the god of the New Testament was much superior and nicer.
One issue with this is that the Old Testament was very handy to the Christian Church. They used many statements from it that can be construed as prophecies, and interpreted them as predicting the rise of Jesus. So the Old Testament gave “support”’to the ideas of the New Testament and the divinity of Jesus.
Good example is Psalm 2:7 http://biblehub.com/psalms/2-7.htm