Churches and Monasteries of Midyat

If you had asked the historic Jesus (assuming he existed) what his religion was (ignoring that the term religion is rather modern), he would have answered Jew. He was not setting out to create a new church. The Jews had had prophets before and they were preaching about the coming of the Messiah, so that's where he would have placed himself. A similar argument can be made for Mohammed by the way.

Eventually, after Jesus passed and it became clearer and clearer that the bulk of the Jews were not accepting Jesus as the Messiah, the religion separated. This was a bit of a problem, though, for the early Christians, as Jesus didn't really create rules to govern a new religion and his church. This was left to apostles and the later clergy.

They had plenty of gaps to fill and dogmas to define. Notable topics are the nature of the trinity (never understood that one, I would be an Arian if anything) or the icons. In addition, there were loads of practical topics to resolve. Several councils were held to address these, the most famous one being the council of Nicaea. If you want a fun read, I recommend the Synod of Laodicea. The very first item (canon) and supposedly the most urgent one is about second wives, secret wives and the communion?!

However, filling the gaps resulted in even more splintering of the Church. Notably, the Byzantine provinces in Syria (Antioch) …