Definition
Occam’s Razor (or the Principle of Parsimony) states that when two or more hypotheses are consistent with the available data, the one that introduces the fewest new assumptions should be preferred. In the original Latin: “Numquam ponenda est pluralitas sine necessitate” (Plurality must never be posited without necessity).
Why It Matters
Occam’s Razor is the “bullshit detector” of science and philosophy. Every new assumption is a potential point of failure; by choosing the simplest path, we maximize the probability of being right. It prevents us from being led down “rabbit holes” of increasingly complex and unlikely conspiracy theories or pseudoscientific explanations. It is the principle of “Epistemic Economy”—ensuring that we don’t spend our intellectual capital on “explanations” that raise more questions than they answer.
Core Concepts
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Assumption Burden: It is a tool for minimizing the “total weight” of unproven premises. Every new assumption decreases the mathematical probability that the overall explanation is correct.
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Simplest Fewest Entities: A common error is thinking the razor demands the fewest number of causes. Hickam’s Dictum (“Patients can have as many diseases as they damn well please”) highlights that multiple known causes are often more probable than one rare or new cause.
- How to read: “The simplest explanation is not necessarily the one with the fewest entities.”
- Meaning: Parsimony means fewer new assumptions, not fewer total causes—multiple known explanations can beat one exotic one.
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The UFO Example: Explaining a light in the sky via known phenomena (hoaxes, weather, psychology) requires zero new assumptions. Explaining it as an alien spacecraft requires a massive new assumption (the presence of visiting extraterrestrials).
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Ad Hoc Immunization: Pseudoscientists often violate the razor by creating a new assumption to explain away every failure of their theory (e.g., “The invisible dragon is also heatless”).