Scientists must accept facts even when they would like them to be different. They must strive to distinguish between what they see and what they wish to see --- for humanity's capacity for self-deception is vast. People have traditionally tended to adopt general rules, beliefs, creeds, theories, and ideas without thoroughly questioning their validity and to retain them long after they have been shown to be meaningless, false, or at least questionable. The most widespread assumptions are the least questioned. Most often, when an idea is adopted, particular attention is given to cases that seem to support it, while cases that seem to refute it are distorted, belittled, or ignored. We feel deeply that it is a sign of weakness to "change out minds." Competent scientists, however, must be expert at changing their minds. This is because science seeks not to defend our beliefs but to improve them. Better theories are made by those who are not hung up on prevailing ones.