Occam's window

TL;DR

When multiple explanations exist, prefer the one that makes the fewest assumptions and is most straightforward.
Favors explanations that rely on established principles and empirical evidence over untestable or supernatural claims.
Applied across fields (examples in science and psychology) to focus on the most direct explanations.

Definition

Occam’s window, also known as the principle of parsimony or the law of parsimony, is a philosophical principle that states that the simplest explanation or solution is usually the correct one. The principle is named after William of Ockham, a 14th century English logician and Franciscan friar, who is credited with its development.

Explanation

When confronted with multiple potential explanations or solutions, Occam’s window advises selecting the most straightforward one. In scientific contexts this means favoring hypotheses that rely on established scientific principles and are supported by empirical evidence rather than explanations that invoke untestable or supernatural forces. In psychological contexts it means preferring proximate, well-established behavioral explanations over more complex, deeper-rooted accounts unless the additional complexity is warranted by evidence.

Examples

Science — origin of the universe

Some people propose the universe was created by a divine being, while others invoke the Big Bang Theory. The Big Bang Theory explains the origin and evolution of the universe as beginning from a singularity that expanded rapidly to form galaxies, stars, and planets. This explanation relies on well-established scientific principles, such as the laws of thermodynamics, and is supported by a wide range of empirical evidence. Belief in a divine creator requires acceptance of supernatural forces and cannot be tested or proven through scientific methods; therefore, according to the principle of parsimony, the Big Bang Theory is presented as the more likely explanation.

Psychology — aggressive behavior

When explaining why someone acts aggressively, some accounts point to deep-seated emotional issues or childhood mistreatment. While those explanations may be true in some cases, the principle of parsimony suggests a more straightforward explanation: the person may be acting aggressively because they feel threatened or are attempting to assert dominance. These explanations are based on well-established psychological principles, such as the fight or flight response, and are considered more direct than invoking deeper emotional histories.

principle of parsimony
law of parsimony
William of Ockham