Christine Caldwell Ames says that what counts as heretical belief changes over time.
It’s very hard to tell why certain differences become unacceptable. And it depends upon context, it depends upon place, time, forms of consensus. Certainly some things are always believed to be unacceptable. For example, the notion that Christ did not really die on the cross, he wasn’t really crucified, it was a mirage, it was just something imaginary, something that was just seen in a false way – this is always a belief that is understood to be beyond the pale.
Others are more adaptable, others do evolve. For example, what we start to see in the Middle Ages is accusations of heresy for those who doubt papal power, who question the expansion of papal power. And this is something that becomes in a sense genuinely heretical, in that it’s understood to refer back to belief. The role of the pope becomes an issue of belief, and so this becomes heretical.
So again, one of the challenges, but one of the rewards for the historian of the inquisition is to figure out the terms by which things become unacceptable. And again, the precise moments why. Why is something that seems to be completely insignificant then seized upon?
And I think another example that might be resonant for modern Christians is, again, the scriptures. That is, the scriptures in the vernacular; what the scriptures actually tell us about the person of Jesus – one of the most famous debates, and debates about heresy, in the Middle Ages is over the poverty of Christ. Was Christ poor? Were his apostles poor? Were they not? And this does become a matter of deep theological and social stress. And we don’t see questions about that really asked until the social and economic circumstances of Europe become such that this becomes an absolutely crucial and feverish issue. Centuries before that, no one thought to ask.