Today I was reading through one of the many books that I have yet to finish--The Trinity by Roger Olson and Christopher Hall.
In particular, I was reading a summary of the development of Trinitarian theology from the patristic era. As I was reading, it suddenly occured to me that it is very easy to become a heretic in one's trinitarian theology. Especially, in the patristic era, or the era of the early church fathers.
At the same time, it is also interesting to note what theological heresies continue to rear their ugly heads over and over again. In particular, I was struck by the human tendency to present the Old Testament God and the New Testament God as almost two different Gods, or two different kinds of Gods. According to this line of thinking, the Old Testament God is Rambo, and the New Testament God is more like Mr. Rogers. There are a million variations of how people communicate this "divine personality change" between the Old Testament and the New Testament. But this understanding of God is unbiblical, heretical, and immoral.
In the early church (or patristic period) this idea was advocated by Marcion, who as a result had a number of beliefs that were very close to gnosticism, and were rejected by the early church councils. Iraneus says of Marcion's beliefs that the Old Testament and New Testament God are different that one cannot "Divide God into two, calling one good and the other just. For in doing so he (Marcion) destroys the divinity of both." (Hall and Olson, p.27) As Gerald O'Collins correctly states "The Jewish Creator God is identical with the Father of our Lord Jesus Christ". (The Tripersonal God, p. 97).
The OT God v. NT God theological approach creates a problem because it allows us to quickly dismiss the bulk of God's Word, or a least not give it as strong of an emphasis. Yet, a quick study of the New Testament demonstrates that the early church used their Old Testament as their primary Scriptures, and through the Old Testament texts were able to see how the message of Jesus was consistent with the God revealed in Scriptures (namely the Old Testament).
Relatedly, even though this was less a concern of the church fathers, this "divine personality change" divorces Jesus from his Hebrew context. And when we divorce Jesus from who he was ethnically, an ancient Jewish peasant/laborer, then it becomes very easy to misunderstand Jesus. Specifically, it can lead to anti-semitical theology and behavior. If you doubt this, study the theology of 18th-early 20th century German theology, which both puts less of an emphasis on the Trinity, and Jesus' Jewish heritage. This poor theology in many ways led to the holocaust.
Ok...enough of me rambling...sometimes I just need to write things down or I forget what I was thinking about.