At this point in my text, I am aware of having to make an abrupt change of mental gear. Previously, my approach has been essentially intellectual. In considering some paranormal claim, I have asked myself, Is this likely to be true? Should I take it seriously? If so, I try to see if an extension of existing physical theory could accommodate it. Now I have to approach notions that have a strong human or emotional element, while retaining as much as I can of that detached and scientific stance. This often seems very difficult. Many of those who oppose the theory of evolution, for example, do so essentially because it offends their religious feelings. They do not care about its likelihood, but find it emotionally repellant. So it is with some diffidence that I begin to compare my notions of the unknown world with the informal beliefs that many people seem to hold about themselves.