Occam's Razor

Occam's Razor (also spelled Ockham) is known as the principle of parsimony or the economy of hypotheses. It is a philosophical principle dictating that, all things being equal, simplicity is preferred over complexity. Traditionally, the Razor has been used as a philosophical heuristic for choosing between competing theories, but the principle is also useful for defining methods for empirical inquiry, selecting scientific hypotheses, and refining statistical models. According to Occam's Razor, a tool with fewer working parts ought to be selected over one with many, provided they are equally functional. Likewise, a straightforward explanation ought to be believed over one that requires many separate contingencies.

For instance, there are a number of possible reasons why a light bulb does not turn on when a switch is flipped: Aliens could have abducted the light bulb, the power could be out, or the filament within the bulb has burned out. The explanation requiring aliens is exceedingly complex, as it necessitates the existence of an unknown life form, a planet from which they have come, a motive for taking light bulbs, and so on. A power outage is not as complicated, but still requires an intricate chain of events, such as a storm, accident, or engineering problem. The simplest of these theories is that the light bulb has simply burned out. All theories provide explanations, but vary in complexity. Until proof corroborating one account surfaces, Occam's Razor requires that the simplest explanation be preferred above the others. Thus, the logical—and most likely correct—hypothesis is that the light bulb has burned out.

This entry begins with a brief history of Occam's Razor. It then discusses the implications for research. The entry concludes with some caveats related to the use of Occam's Razor.