Considered Opinions vs. Tested Opinions

Was just reading re: Hariet Miers over at Prof. Bainbridge's blog, when I read this--a bit of a missive sent by a Harvard law prof:

If Harrier Miers has to study and reflect, now, in order to develop a personal theory of the Commerce Clause, how can we possibly have any confidence that she'll remain committed to that theory five, ten, or twenty years from now? First impressions are often wrong, even when we've put lots of thought into them. Unless and until Miers has publicly defended her theory against aggressive testing by very smart people who take a different view, we can't know have any confidence that she can do so -- and, thus, that she won't abandon it somewhere down the road. And therein lies the problem -- or at least one of the problems.

The truth contained in this short paragraph is profound, and it's really true of opinion in general, regardless of the field. Theology is what I'm thinking about in this case. Considered opinions must be submitted to, and survive, energetic critique before their holder can really say that it is what he really and truly believes. Adversity is the true test of how deeply held an opinion is. How many people out there believe something simply because they have never been challenged about it? In other words, how many opinions are actually intellectual defaults as opposed to formed opinions.?