"Really, Watson, you excel yourself," said Holmes, pushing back his chair and lighting a cigarette. "I am bound to say that in all the accounts which you have been so good as to give of my own small achievements you have habitually underrated your own abilities. It may be that you are not yourself luminous, but you are a conductor of light. Some people without possessing genius have a remarkable power of stimulating it. I confess, my dear fellow, that I am very much in your debt."
Sherlock Holmes to Watson in The Hound of the Baskervilles
Christian theology is not a completed project but an ongoing journey. Along that journey many of us take wrong turns and head up blind alleys. Sometimes those alleys are a harmless waste of time, other times they are more serious, leading to what the church comes to consider heresy.
But we need to be clear of a few things about heresy:
1. Those who embrace what come to be seen as heretical opinions are usually sincere people in pursuit of the truth of God in Christ. That are not trying to "distort the truth" or deceive people. The church may come to discern serious problems in the positions espoused but that should not be taken to mean that those who embrace heretical positions do so as a result of a desire to lead people astray. Even a smidgen of knowledge about Apollinarius, for instance, would reveal that he went astray in his very attempt to defend Nicene orthodoxy and oppose Arius.
2. The pursuit of truth will often lead to dead ends and sometimes those ends are judged heretical but that does not mean that the routes were not worth exploring nor that they are obviously "dumb." Heretical views always spring from some genuine insights into God and usually have some sensible logic underpinning them.
3. Even in matters heretical some heresy is worse than other heresy. For instance, Docetism (which denies the humanity of Jesus) and Arianism (which denies the divinity of Jesus) are worse than Nestorianism (which affirms both but, in spite of Nestorius' best intentions, failed to do justice to the unity of Christ).
4. Indeed, the heretics offer a gift to the church for it is the very exploration of certain theological dead-end routes that enables the church to clarify its own thinking on the matters concerned. To corrupt Holmes, heresy may not possess "genius" but it can stimulate "genius" in others. Without various Christological heresies the church would not have clarified some central matters about the person of Christ and of the Trinity, for instance.
5. Holding heretical opinions does not make one a heretic. If that were the case LOADS of Christians would be heretics. I know plenty of Christians (including Christian leaders) who are holding heretical views without realizing it. To be a heretic one must know that the opinion runs counter to the mind of the church and still hold on to it in spite of that.
So I am glad for the presence of those who come to be designated heretics in so far as their provocations help the church to clarify its own mind. They were, for the most part, sincere people with some sensible ideas that deserved exploring.
I am less pleased when some Christians return to heretical opinions after their problems have been exposed and the church has rejected them. That, to quote Proverbs, is like a dog returning to its vomit.