when two competing hypotheses explain the data equally well, choose the simpler. Or, as Sir William Hamilton puts it, "Neither more, nor more onerous, causes are to be assumed, than are necessary to account for the phenomena." Named for English philosopher William of Ockham or Occam (c.1285-c.1349), who expressed it with Entia non sunt multiplicanda praeter ncccssitatem.
So called after William of Occam (died about 1349): but, as a historical fact, Occam does not make much use of this principle, which belongs rather to the contemporary nominalist William Durand de St. Pourçain (died 1332). [Century Dictionary]
|Occam's razor or Ockham's razor|
A rule in science and philosophy stating that entities should not be multiplied needlessly. This rule is interpreted to mean that the simplest of two or more competing theories is preferable and that an explanation for unknown phenomena should first be attempted in terms of what is already known. Occam's razor is named after the deviser of the rule, English philosopher and theologian William of Ockham (1285?-1349?).
The English philosopher, William of Occam (1300-1349) propounded Occam's Razor:
Entia non sunt multiplicanda praeter necessitatem.
(Latin for "Entities should not be multiplied more than necessary"). That is, the fewer assumptions an explanation of a phenomenon depends on, the better it is.
For example, some claim that God caused himself to exist and also caused the universe to exist - he was the "first cause" - whereas Occam's Razor suggests that if one accepts the possibility of something causing itself then it is better to assume that it was the universe that caused itself rather than God because this explanation involves fewer entities.
The negation of Occam's Razor would suggest that an arbitrarily complex explanation is just as good as the simplest one. (E.g. God and his cat created a robot called Sparky who built the universe from parts bought from a shop in another dimension).
See also KISS Principle.