heresy and haeresis

A heretic is literally a chooser - one who chooses between a variety of faith positions. This is anathema in Christianity because, after the Diocletianic persecutions, the survivors couldn't find anyone to set up a church with, because they all believed different stuff; and so it was decided to have a creed that all Christians could subscribe to (this was finally codified at the Council of Nicaea, 325 CE). In subsequent centuries theology became ever more codified, until there was a bewildering variety of heretical positions to choose from.

Haeresis (the word from which heresy is derived), in the ancient pagan world, appears to have meant a school of thought. The tolerant attitude of ancient pagans is summed up by Quintus Aurelius Symmachus (a hero of mine):

Everything is full of gods. Whatever men worship, it may fairly be called one and the same. We all look up to the same stars; the same heaven is above us all; the same universe surrounds every one of us. What does it matter by what system of knowledge each one of us seeks the truth? It is not by one single path that we attain to so great a secret.

- Quintus Aurelius Symmachus