Note: the following has been abstracted from the Grolier Encyclopedia.

Occam's Razor

Occam's razor is a logical principle attributed to William of Occam, although it was used by some scholastic philosophers prior to him. The principle states that a person should not increase, beyond what is necessary, the number of entities required to explain anything, or that the person should not make more assumptions than the minimum needed. This principle is often called the principle of parsimony. Since the Middle Ages it has played an important role in eliminating fictitious or unnecessary elements from explanations. In the development of logic, logicians such as Bertrand Russell removed traditional metaphysical concepts by applying Occam's razor. Questions have been raised, however, as to whether a person can determine without any doubt that given entities or assumptions are not needed in an explanation. Unless this determination can be made, it is impossible to tell with complete certainty when the principle can be applied.