Also called the principle of simplicity, Occam’s razor is often referred to by sceptics commenting on investigations of the paranormal. This principle essentially states that when several explanations for a phenomenon are possible, it is always best to choose the simplest one. For example, if a person sees a shiny metal object flying across the sky, the simplest explanation would be that the object is an airplane rather than an extraterrestrial spacecraft.
Using Occam’s razor, choosing to explore the theory that UFOs are extraterrestrial spacecraft would be foolish because this theory would require many assumptions, including the notion that extraterrestrials exist, that they are intelligent, that they are capable of space travel, that their planet is close enough for them to visit Earth, and that they would want to visit Earth. The basic point of Occam’s razor, which is that in developing theories people should make as few assumptions as possible, is typically expressed with the Latin phrase Entia non sunt multiplicanda praeter necessitatem, which means “Entities should not be multiplied beyond necessity.” This was first proposed by a fourteenth-century English friar, William of Ockham, and it has since been used by theorists in all branches of science.
The Greenhaven Encyclopedia of Paranormal Phenomena – written by Patricia D. Netzley © 2006 Gale, a part of Cengage Learning