Hanlon’s razor is an aphorism expressed in various ways including “Never attribute to malice that which is adequately explained by stupidity,” — or “Don’t assume bad intentions over neglect and misunderstanding.” It recommends a way of eliminating unlikely explanations for a phenomenon (a philosophical razor).
As an eponymous law, it may have been named after Robert J. Hanlon. There are also earlier sayings that convey the same idea dating back at least as far as Goethe in 1774.
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.
Goethe’s The Sorrows of Young Werther (1774): “Misunderstandings and neglect create more confusion in this world than trickery and malice. At any rate, the last two are certainly much less frequent.”
Jane West’s The Loyalists (1812): “Let us not attribute to malice and cruelty what may be referred to less criminal motives. Do we not often afflict others undesignedly, and, from mere carelessness, neglect to relieve distress?”
A common (and more laconic) British English variation, coined by Bernard Ingham, is the saying “cock-up before conspiracy,” deriving from this 1985 quotation: “Many journalists have fallen for the conspiracy theory of government. I do assure you that they would produce more accurate work if they adhered to the cock-up theory.”
Another similar instance from politics is the attribution by First Minister of Scotland, Henry McLeish, of financial irregularities that led to his resignation in 2001, to “a muddle not a fiddle.”
“Heinlein’s Razor” has since been defined as variations on “Never attribute to malice that which can be adequately explained by stupidity, but don’t rule out malice.” This quotation is falsely attributed to Albert Einstein in Peter W. Singer’s book Wired for War (2009).