Hanlon's razor is an aphorism expressed in various ways, including:
- Never attribute to malice that which is adequately explained by stupidity.
It suggests a way of eliminating unlikely explanations ("attributions") for human behavior and its consequences. Statements of this kind are known as philosophical razors. It is an eponymous law, probably named after the writer Robert J. Hanlon.
Inspired by Occam's razor, the aphorism was popularized in this form and under this name by the Jargon File, a glossary of computer programmer slang. In 1990, it appeared in the Jargon File described as a "'murphyism' parallel to Occam's Razor". Later that same year, the Jargon File editors noted lack of knowledge about the term's derivation and the existence of a similar epigram by William James. In 1996, the Jargon File entry on Hanlon's Razor noted the existence of a similar quotation in Robert A. Heinlein's short story "Logic of Empire" (1941), with speculation that Hanlon's Razor might be a corruption of "Heinlein's Razor". (A character in Heinlein's story described the "devil theory" fallacy, explaining, "You have attributed conditions to villainy that simply result from stupidity.")
In 2001, Quentin Stafford-Fraser published two blog entries citing e-mails from one Joseph E. Bigler about how the quotation originally came from Robert J. Hanlon of Scranton, Pennsylvania, as a submission for a book compilation of various jokes related to Murphy's law published in Arthur Bloch's Murphy's Law Book Two: More Reasons Why Things Go Wrong! (1980). Subsequently, in 2002, the Jargon File entry noted the same, though not definitively.
"Heinlein's Razor" has since been defined as variations on "Never attribute to malice that which can be adequately explained by stupidity."
- Andrew S. Wigosky (2004). RAPID Value Management for the Business Cost of Ownership. Digital Press. p. 5. ISBN 9781555582890.
[...] Hanlon's Razor: 'Never attribute to malice that which can be adequately explained by stupidity.' This definition comes from 'The Jargon File' (edited by Eric Raymond), but one poster attributes it to Robert Heinlein, in a 1941 story called 'Logic of Empire.'
- Livraghi, Giancarlo (2004). Il potere della stupidità. Pescara, Italy: Monti & Ambrosini SRL. p. 1. ISBN 9788889479131.
- "Hanlon's Razor". Jargon File. Eric S. Raymond. 2002-03-03. Retrieved 2017-07-19.
- Guy L. Steele; Eric S. Raymond, eds. (1990-06-12). "The Jargon File, Version 2.1.1 (Draft)". jargon-file.org. Retrieved 2017-07-19.
- Eric S. Raymond; Guy L. Steele, eds. (1990-12-15). "The Jargon File, Version 2.2.1". jargon-file.org. Retrieved 2017-07-19.
- Eric S. Raymond, ed. (1996-07-24). "The Jargon File, Version 4.0.0". jargon-file.org. Retrieved 2017-07-19.
- Stafford-Fraser, Quentin (2001-11-26). "[untitled]". Retrieved 2017-07-19.
- Stafford-Fraser, Quentin (2001-12-04). "The origins of Hanlon's Razor". Retrieved 2017-07-19.
- Arthur Bloch (1980). Murphy's Law Book Two: More Reasons Why Things Go Wrong!. Price Stern Sloan. p. 52. ISBN 9780417064505.
- Eric S. Raymond, ed. (2002-03-03). "The Jargon File, Version 4.3.2". jargon-file.org. Retrieved 2017-07-19.