Occam’s razor (also Ockham’s razor; Latin: lex parsimoniae “law of parsimony“) is a problem-solving principle attributed to William of Ockham (c. 1287–1347), who was an English Franciscan friar, scholastic philosopher, and theologian. His principle states that among competing hypotheses, the one with the fewest assumptions should be selected.

In science, Occam’s razor is used as a heuristic guide in the development of theoretical models, rather than as a rigorous arbiter between candidate models.^[1][2] In the scientific method, Occam’s razor is not considered an irrefutable principle of logic or a scientific result; the preference for simplicity in the scientific method is based on the falsifiability criterion. For each accepted explanation of a phenomenon, there may be an extremely large, perhaps even incomprehensible, number of possible and more complex alternatives. Since one can always burden failing explanations with ad hoc hypotheses to prevent them from being falsified, simpler theories are preferable to more complex ones because they are more testable.^[3][4][5]