It was kind of settled in the Council of Nicaea and by Emperor Constantine. That council and his efforts are worth reading about. It’s part of the reason the LDS church has a problem with what the Christian community believes and why none of the Christian denominations accept the LDS as Christian (they rejected us we didn’t reject them). I think it was Orgin that believed in reincarnation and there were all kinds of fights about the nature of Jesus (a man, totally divine, created by God which makes Jesus a creature not a child, etc) Every line in the Nicene Creed was fought over and is a dense theological statement. You need to study it line by line and find out why it was written that way and what heresy(ies) it was addressing. It underlies pretty much all future theology and fights over theology. I’ve noticed that the Methodist Church here on the Left Coast has been downplaying it and the earlier creeds in favor of the “social creeds”. It would require a lot of teaching to get the people to understand the what and why of what they were reading and saying. I’ve got to think about it, but it might put the brakes on some of the liberal theology that is being pushed here on the left coast as well. Time for more study.
Heresies existed before and after the Council of Nicaea. Man trying to explain the nature of God is always tough. It was over heresies and sharing of power that the Eastern Orthodox split from the Catholic Church. Protestantism was founded on heresies (in eyes of Catholic Church) and they haven’t been reconciled to this day which is why the Catholic Church doesn’t recognize communion in the Protestant Churches and if you’re a Protestant you aren’t supposed to take Communion in a Catholic Church (honestly, I think it’s now about power and tradition than it is about important things. I’m about 100% sure that the Calvinists and Presbyterians no longer believe in predestination for example. To me that’s a major heresy, but I’m a Methodist we’re like the Anglican and Catholic Church and don’t accept predestination at all)
Then you'd be 100% wrong.
If you generalize from liberal Presbyterians (like the PCUSA) to all Presbyterian churches or to the larger Calvinistic movement, then I can see why you have this misunderstanding. Otherwise, I'd have to ask you where you got your information.
To me that’s a major heresy
It's not my intent to highjack this thread but since you place so much emphasis on church councils, you might want to review what happened at the Synod of Dordt. In what was the most ecumenical of all Protestant councils to date, the question of what became known as "The Five Points of Calvinism" was debated. The council ruled that the orthodox position was the Calvinistic position including the position on predestination (see "The First Main Point of Doctrine" in the Canons of Dort).