Here's a bit of bizarre but fascinating church history for you: the New Yorker has a detailed overview of the life and death of Giordano Bruno, a sixteenth-century heretic burned at the stake by the Inquisition for his strange (and in some ways scientifically prescient) understanding of the cosmos. One of his basic ideas was that the universe was infinitely vast, a proposal which (along with his other unorthodox views) was seen as contradictory to the Church's belief that Earth and mankind were the central components of God's Creation:
Inconveniently, that vision was heresy from end to end. If there were countless worlds besides ours, this sidelined the Christian story. Creation, expulsion, salvation: such things might have happened, but somewhere off in a corner, while other things were happening on other planets. Also eliminated was God’s difference from humanity. If, as Bruno saw it, God was present in every atom of the universe, then transubstantiation became a silly idea. (God was already in the wine.) Ditto incarnation. Bruno later said that he started having doubts about Jesus at the age of eighteen; in his mature philosophy, the Messiah has no place. Nor does original sin, or pretty much any sin. God “makes his sun rise over good and bad,” Bruno wrote. Even devils were going to be pardoned. To lead a virtuous life, you had only to do unto others as you would have them do unto you. As the reader may have noticed by now, much of this constitutes liberal Christian thought in our time. (What Bruno discarded was the Church’s literalism—exactly what many of today’s believers have done.) Likewise, Bruno’s cosmology anticipated modern physics and astronomy. But it did not accord with the views of the sixteenth-century Church. It sounded like Protestantism, or worse.
He certainly was a character; he sounds like somebody straight out of an Umberto Eco novel. (As a matter of fact, my only other knowledge of Bruno comes from John Crowley's Aegypt novels, in which he is a central character.)
I mostly just wanted to pass this along to you because it's curious church history, but a thought occurs to me as I re-read this mini-biography: it's interesting how very seriously ideas were taken in Bruno's time; the theological implications of his ideas alone were enough to make him a threat. Ideas were perceived to have real power in and of themselves.
Anybody else have a "favorite" heretic from church history—somebody whose rebellion against orthodox Church beliefs fascinates you?