Because thinking is for doing, we search for evidence that supports our opinions, not the other way around.

Topic: The Role of Self-righteousness
Jonathan Haidt: Self-righteousness refers to our general tendency to give ourselves the benefit of the doubt, combined with our extraordinary ability as reasoning creatures to employ reason only to reach the conclusions we want to reach. That's the general rule about reasoning. Thinking is for doing. We employ our reasoning to reach the conclusions we want to reach.
So if we're mad at someone, we very easily find reasons why they're wrong and we're right. So this is just part of the nature of who we are.
I think this helps us to understand a lot about our current political situation, about the nastiness of our political divides, and why it is that it's just so hard for us to see that there is wisdom on both sides of almost any long standing question.
This is the most important lesson I learned in writing "The Happiness Hypothesis", is that if you're a liberal, you're not going to learn much by reading more liberal writing. Pick up some conservative magazines. Pick up some conservative thinkers. There's revelation after revelation. There's a lot of good ideas over there and, of course, vice versa.
But my point is we only seek out conclusion. We only seek out evidence that supports the conclusion we want to reach, and therefore we deprive ourselves of most of the interesting ideas in the world.
 
Recorded on May 9, 2008.