"I don't know" is not an apology. There's no shame. It's a simple statement of fact. When Richard Feynman didn't know, he often worked harder than anyone else to find out, but while he didn't know, he said, "I don't know." [...]
What makes me libertarian is what makes me an atheist -- I don't know. If I don't know, I don't believe.This is Penn Jillette of Penn & Teller in CNN.com.