Let’s see if I can explain Bilateral Ecclesiology: Imagine that God has a people. A very special group of people. Now later, God tells his son to go to his special people. When his son arrives, he chooses a new special people. Now God has 2 special peoples.
That's Bilateral Ecclesiology in a nutshell. In case you didn't figure it out, God's "2 special peoples" are the Jewish people (God's chosen people from old) and the Church (His son's chosen people). Bilateral = "two groups". Ecclesiology = "theology about the ekklesia, the assembly of people". A simpler name of this belief might be "Two Church": it believes that God has 2 assemblies: the Christian Church, and the Jewish people.
An interesting outcome of this theology is separation: If God has 2 special peoples, then we shouldn't blur the line between Special People A and Special People B. There's an example in Scripture where a tribe called the Galatians -- part of theoretical Special People B -- thought they had to undergo the old Special People A ritual in order to be approved by God. Paul, a follower of the aforementioned son, wrote a letter to these Galatians, and basically tore them a new one.
"You crazy people! Don't you know God accepts you without having to do the Special People A ritual?! I say that if you undergo Special People A ritual, you may as well never have heard about God’s son."
In concrete terms, Paul the apostle of Jesus was telling gentiles they didn't need to convert to Judaism and become Jewish in order to gain God's approval. So maybe the Bilateral Ecclesiology folks have a point about all this separation stuff?
Well, Bilateral Ecclesiologists...ermm, I'm going to call them Two Churchers for simplicity. Two Churchers are all about preserving distinctions between Special People A and Special People B. This has resulted in a funny little thing: when they see Special People B (gentiles) keeping the Torah (God's agreement with Special People A), they cry, "Supersessionism!"
(Doesn't this all sound utterly ridiculous thing to argue about? Religious people are stupid and wasteful and totally spend way too much time arguing about silly things. Yes, we should be spending our time on more important things like feeding the poor and helping people. But here we are...)
Supersessionism. It's the "Special People B replace Special People A" idea. B replaces A. Christians replace Israel. Bilateral Ecclesiologists hate this thing. (I do too!) We hate it because it has resulted in persecution of Jewish people by Christians: Just 90 years ago, for example, a Catholic leader in the Vatican wrote that because they rejected God's son, Jews were forever cursed to be wandering nomads without nation. He wasn’t the first to make that claim, either. (Guess they were wrong.)
So supersessionism, replacement theology, is bad. God hasn't replace the Jews. And there's pretty good evidence in the Christians Scriptures that suggest he's not replaced Jewish people. Paul, that same guy who tore the Galatians a new one, said of Jews:
"God has not forsaken his people whom he foreknew. I'm a Jew myself! There's a temporary hardening of hearts here. It'll go away eventually, but it's being used by God to bring in the gentiles."
Back to Two Churchers: while they rightfully disdain supersessionism, they're prone to seeing supersessionism everywhere. It's like the Hebrew Roots paganoia, except with supersessionism. Gentile saying the Shema? Supersessionism. Gentiles celebrating Passover? Supersessionism. Gentile giving the Aaronic blessing out of Deuteronomy? Supersessionism. Singing to music instead of traditional prayers? Supersessionism. Filling grandma's prescriptions? You get the idea.
Another criticism of Two Church is that the idea doesn't really have support in the New Testament. We don't see in the New Testament, for example, gentiles and Jews meeting in separate assemblies. On the contrary, it records gentiles meeting in the synagogues; and only 1 "assembly" is mentioned: Messiah's assembly. If there was separation between Yeshua's followers at an assembly level, the New Testament is silent on it.
In practice, this leads to accusations of exclusion, racism, and feelings of inferiority: non-Jews are encouraged to go back to Special People B places -- Christian Churches -- so that Special People A, the Jews, can have their distinctions and separations, avoiding assimilation into Special People B.
This has led to conversions and proselytism (Special People B want to join Special People A), but also has resulted in apostasy. More on that in the next post.