The Pedagogical Value of Error

I have been thinking recently of the Christian doctrine, commonly found, but due in its most common form probably to St. Hilary of Poitier, that God stirs up heresy, or allows heresy to be stirred up, in order to force the Church to grow and deepen its understanding of things that it is growing complacent about. I think this is a very powerful truth, not only for heresy in particular, but for error in general. That is: error is an opportunity for teaching and learning. I think people, faced with errors, tend to get very frustrated with them because they are perpetually trying to convince the people with the erroneous views. But as far as teaching goes, it isn't important at all whether you convince others; what is important instead is that you impress them, or, rather, that you put forward the subject matter itself and let the subject matter impress and convince them. If put forward correctly, it will always do a better job of convincing people than you ever will, anyway. And even if you don't convince anyone, even if after all your efforts it turns out that you are only preaching to the choir - well, the choir may be on your side, but they often need a bit of preaching, too. One thinks of the 'intelligent design' controversy. Do people magically gain special insight into scientific issues merely on the basis of whether they agree with a given side? It is, for all that it must frustrate some people, one of the greatest teaching opportunities of all time; and even if one ends up convincing no one on the other side, there are a lot of people who will learn a great deal from it. And one might learn a few unexpected things oneself. So it's a general principle: error is our occasion and our opportunity for deepening our understanding of the world. It will always be something of an evil (I can think of more than a few errors that I wish I could stamp out entirely); but it is not an unambiguous evil. And that's a relief, I think.