To me, that's the sign of close mindedness. It's only natural to change your beliefs from time to time, especially when confronted with damn good questions that you can't answer. You have to constantly question your beliefs, to see if they really fit in with reality. When reality seems to contradict your beliefs, you ought to seriously examine the facts, to try to find out if you're really wrong or if your information is. I find myself changing my mind a lot to fit the facts I'm presented with. My world outlook is constantly changing as experience continually provides me with a clearer picture of reality. I haven't always believed what I believe now, you know. Why just a few years ago I was a Marxist, and a few years before that I was a Christian. I'm not ashamed to admit that I've believed some really outlandish ideas over the course of my life. Alien abductions, ESP, ghosts, prophecies about the end of the world, Santa Claus, the Tooth Fairy...but as my mind has matured I have rejected those beliefs that didn't fit in with what I've learned about the world. Steadfast dogmatism is nothing to be jealous of.

“In science it often happens that scientists say, ‘You know that's a really good argument; my position is mistaken,’ and then they would actually change their minds and you never hear that old view from them again. They really do it. It doesn't happen as often as it should, because scientists are human and change is sometimes painful. But it happens every day. I cannot recall the last time someting like that happened in politics or religion.” —Carl Sagan