We said that schism divides a religion outwardly but not inwardly, and for this reason it can be seen as legitimate. But that doesn’t mean that all religious disagreements are valid and are only a matter of adaption. Error is very real, hence the very real problem of heresy. The difference is simply that heresy divides or alters or limits the spirit of the religion. That is why it is right to reject it, not simply as an inappropriate formulation, but as a dangerous error.