In philosophy, a razor is a principle or rule of thumb that allows one to eliminate (shave off) unlikely explanations for a phenomenon, or avoid unnecessary actions. Common examples include:
Alder's razor (also known as Newton's flaming laser sword): If something cannot be settled by experiment or observation, then it is not worthy of debate. Grice's razor (also known as Guillaume's razor): As a principle of parsimony, conversational implicatures are to be preferred over semantic context for linguistic explanations. Hanlon's razor: Never attribute to malice that which can be adequately explained by stupidity. Hitchens' razor: That which can be asserted without evidence can be dismissed without evidence. Hume's guillotine: What ought to be cannot be deduced from what is; prescriptive claims cannot be derived solely from descriptive claims, and must depend on other prescriptions. Hume's Proportionality of Cause: "If the cause, assigned for any effect, be not sufficient to produce it, we must either reject that cause, or add to it such qualities as will give it a just proportion to the effect." Occam's razor: Explanations that require fewer assumptions are more likely to be correct; avoid unnecessary assumptions. Popper's falsification criterion of demarcation: For a theory to be considered scientific, it must be falsifiable. Sagan standard: Positive claims require positive evidence, extraordinary claims require extraordinary evidence.
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