McArdle has a great post about the arrogance of graduate students.

But I have to agree with some of her commenters. This is a far more common attitude among social science grad students than physical science ones. I know my share of arrogant physicists and astronomers, but the ratio is much smaller. The reason is because science itself is very humbling. I think I’m pretty smart — the test scores say so — but grad school sometimes made me feel like an idiot and nature always does. There’s nothing to take your ego down like having a paper turn out to be complete bullshit — or seeing a paper by a respected peer turn out to be bullshit. Nature has a way of proving us wrong over and over again. It’s difficult to think you know everything when you are confronted by your ignorance on a daily basis.