There are difficulties for forming sound beliefs about complex subjects. The evidence about them is often complex, and subject to misinformation, and the beliefs formed about them are often too simple and wishful. The beliefs of young children are fallible in all the usual ways. Some ideas come naturally to children and seem to be evolved adaptations. These may be the sources of the paranormal beliefs that are common among adults. Some parts of the brain are active during dreaming sleep and other functions are inactive. Disbelief is inactive, and the loss of its restraining effect on chains of association of ideas may be why absurdities arise and are accepted.