A philosophical razor is a rule of thumb that helps us “shave away” unnecessary, weak, or unproductive explanations. Razors do not prove that an explanation is true; they help us decide which explanations deserve attention first. There is no official or universally accepted list.
The most useful philosophical razors
| Razor | Basic principle | Simple example |
|---|---|---|
| 1. Occam’s Razor | Prefer the explanation requiring the fewest unsupported assumptions. | Your computer will not start. A dead battery is more likely than a sophisticated hacker disabling it. |
| 2. Hanlon’s Razor | Do not attribute something to malice when it can be adequately explained by error, ignorance, or incompetence. | A coworker failed to invite you to a meeting. They may have forgotten rather than deliberately excluded you. |
| 3. Hitchens’s Razor | A claim made without evidence may be dismissed without evidence. | Someone claims an invisible creature caused a power failure but offers no evidence. You do not have to disprove it. |
| 4. Sagan Standard | Extraordinary claims require correspondingly strong evidence. | “I saw a dog outside” needs little verification; “I saw a dog speaking English” requires much stronger evidence. |
| 5. Alder’s Razor | Do not spend excessive time debating claims that cannot produce observable or logically demonstrable consequences. | Two people argue about an undetectable force that affects absolutely nothing. There may be no way to settle the debate. |
| 6. Grice’s Razor | In language, prefer an explanation based on context and implied meaning before assuming a word has a new literal meaning. | “Can you open the window?” is normally a request, not merely a question about physical ability. |
| 7. Morgan’s Canon | Do not explain behavior through complex mental abilities when simpler learning processes adequately explain it. | A dog opening a gate may have learned through trial and error rather than carefully reasoning like a human. |
1. Occam’s Razor — minimize assumptions
Occam’s Razor is often summarized as “the simplest explanation is usually correct,” but that wording can be misleading. It really means:
When two explanations account for the evidence equally well, prefer the one that introduces fewer unnecessary assumptions.
For example:
- Explanation A: Your keys are missing because you left them at work.
- Explanation B: A burglar secretly entered your house, moved only your keys and left without taking anything.
Explanation A requires fewer unsupported assumptions.
Occam’s Razor does not mean that reality must always be simple. A complicated explanation may be correct when the evidence requires it.
2. Hanlon’s Razor — mistake before conspiracy
Hanlon’s Razor says:
Never attribute to malice what can be adequately explained by stupidity.
“Stupidity” here can include carelessness, misunderstanding, poor communication, forgetfulness or lack of competence.
Suppose a government website repeatedly fails. Possible explanations include:
- Officials deliberately want to frustrate citizens.
- The system is outdated, poorly designed and understaffed.
Hanlon’s Razor advises examining the ordinary explanation before assuming malicious intent. It does not say that malice never occurs—only that it should not be your automatic conclusion.
3. Hitchens’s Razor — the claimant carries the burden
Hitchens’s Razor states:
What can be asserted without evidence can be dismissed without evidence.
If someone claims that a particular crystal can cure every disease, the responsibility is on that person to produce credible evidence. You are not required to prove that every possible magical mechanism is impossible.
It does not mean that every unproven idea is false. It means that you are not rationally obligated to accept it until adequate reasons or evidence are presented.
4. The Sagan Standard — match evidence to the claim
The Sagan Standard says:
Extraordinary claims require extraordinary evidence.
A claim is “extraordinary” when it conflicts strongly with well-established knowledge or has a very low initial probability.
For example, a blurry photograph might be adequate evidence that someone attended a party. The same blurry photograph would not be adequate evidence that extraterrestrials visited the party.
The word extraordinary can be subjective, however. A better interpretation is: the less plausible a claim initially appears, the stronger the evidence needed to justify believing it.
5. Alder’s Razor — make the debate testable
Alder’s Razor is humorously known as Newton’s Flaming Laser Sword. Its weaker and more reasonable version says that we should avoid prolonged disputes unless the competing claims have observable consequences or can be examined through precise reasoning.
For example:
“An invisible object exists outside the universe, but it can never affect anything, be detected or produce any consequences.”
If nothing could possibly count for or against the claim, debating it may not produce knowledge.
This razor is useful in science but can be too restrictive when applied to morality, meaning, aesthetics or political philosophy, where questions may still matter even when laboratory testing is impossible.
6. Grice’s Razor — context before extra meanings
Grice’s Razor concerns language:
Prefer explanations based on conversational implication before inventing additional literal meanings for words.
Suppose someone says:
“Some employees completed the training.”
Listeners may infer that not all employees completed it. But the word some does not literally mean some but not all in every situation. The “not all” meaning may come from conversational context rather than the dictionary meaning of some.
Grice’s Razor therefore helps linguists distinguish between what words literally mean and what speakers imply through context.
7. Morgan’s Canon — avoid overinterpreting behavior
Morgan’s Canon is not normally called a razor, but it serves the same purpose in animal psychology:
Do not interpret animal behavior using higher mental processes when simpler processes adequately explain it.
A dog that learns to open a gate may appear to understand locks and mechanical design. But observation might reveal that it learned the behavior gradually through repeated trial and error.
Modern researchers use this principle carefully because the opposite mistake is also possible: insisting on a simplistic explanation even when strong evidence supports sophisticated animal cognition.
Two closely related filtering principles
Hume’s Guillotine
You cannot logically derive an “ought” solely from an “is.”
For example:
- Fact: Competition occurs in nature.
- Unsupported conclusion: Therefore, humans ought to organize society around ruthless competition.
A moral premise is needed to move from a factual description to a moral obligation. Hume’s Guillotine is not usually called a razor, but it eliminates invalid moral reasoning.
Popper’s falsifiability principle
A scientific theory should expose itself to possible disproof. A claim that explains every conceivable outcome—and can never be contradicted by evidence—has limited scientific value.
For example:
“My prediction is always correct, even when events appear to contradict it.”
Such a claim protects itself from testing rather than explaining reality.
A practical sequence for using them
When hearing a surprising claim, ask:
- What evidence supports it? — Hitchens
- Is the evidence strong enough for such a surprising claim? — Sagan
- Is there a simpler explanation with fewer assumptions? — Occam
- Am I unnecessarily assuming bad intentions? — Hanlon
- Can the disagreement actually be tested or settled? — Alder
Together, these razors help us remain skeptical without becoming cynical: demand evidence, minimize assumptions, avoid imaginary conspiracies and remain willing to revise conclusions when better evidence appears.
