Rule of thumb

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The English phrase rule of thumb refers to a principle with broad application that is not intended to be strictly accurate or reliable for every situation. It refers to an easily learned and easily applied procedure or standard, based on practical experience rather than theory.[1][2]

The use of the phrase as denoting a rough measurement can be traced back to the seventeenth century. A modern folk etymology holds that the phrase derives from the maximum width of a stick allowed for wife-beating under English law; this belief can be traced back to a rumored statement by the eighteenth-century judge Sir Francis Buller that a man may beat his wife with a stick no wider than his thumb.

The English jurist William Blackstone wrote in his Commentaries on the Laws of England of an "old law" that once allowed "moderate" beatings by husbands, but did not mention thumbs or any specific implements. While wife beating has never been legal in the United States, several nineteenth-century court rulings in that country referred to an "ancient doctrine" allowing husbands to physically punish their wives, using implements no thicker than their thumbs.

The exact phrase rule of thumb first became associated with domestic abuse in the 1970s, after which the spurious legal definition was cited as factual in a number of law journals, and the U.S. Commission on Civil Rights published a report on domestic abuse titled "Under the Rule of Thumb" in 1982.


The exact origin of the phrase rule of thumb is uncertain.[3] Its earliest (1685) appearance in print comes from a sermon by British preacher James Durham: "Many profest Christians are like to foolish builders, who build by guess, and by rule of thumb (as we use to speak), and not by Square and Rule".[2][4]

The phrase is also found in Sir William Hope's The Compleat Fencing Master, 1692: "What he doth, he doth by rule of Thumb, and not by Art".[5] James Kelly's The Complete Collection of Scottish Proverbs, 1721, includes: "No Rule so good as Rule of Thumb, if it hit",[6][7] meaning a practical approximation.[5]

Historically, the width of the thumb, or "thumb's breadth", was used as the equivalent of an inch in the cloth trade; similar expressions existed in Latin and French as well.[4][6] Ebenezer Cobham Brewer writes that in some places the thumb was used to gauge the heat of a brewer's vat.[1] According to Phrasefinder, "The phrase joins the whole nine yards as one that probably derives from some form of measurement but which is unlikely ever to be definitively pinned down".[3]

Folk etymology

Cartoon of Sir Francis Buller in judges' robes and powdered wig, carrying bundles of rods; in the background, a man with a rod raised over his head is about to strike a woman who is running away from him
Cartoon by James Gillray satirizing Sir Francis Buller, 1782: "Judge Thumb; or, Patent Sticks for Family Correction: Warranted Lawful!"

A modern folk etymology relates the phrase to domestic violence via an alleged rule under English law that allowed for wife-beating provided the implement used was a rod or stick no thicker than a man's thumb.[5][8][9]

The English jurist William Blackstone wrote in the late 1700s in his Commentaries on the Laws of England that by an "old law", a husband was justified in using "moderate correction" against his wife, but was barred from inflicting serious violence. According to Blackstone, by the late 1600s this custom was in doubt, and a woman was by then allowed "security of the peace" against an abusive husband (he did not mention either thumbs or sticks).[6][8] The twentieth-century legal scholar William L. Prosser, citing Blackstone, wrote that there was "probably no truth to the legend" that a husband or father was allowed to beat his wife "with a stick no thicker than his thumb".[6]

The association between the thumb's width and implements of punishment can be traced to the year 1782, when the English judge Sir Francis Buller was rumored to state that a husband could beat his wife, provided he used a stick no wider than his thumb.[a] There is no recorded proof that Buller ever made such a statement;[4][10] nevertheless, the rumor generated much satirical press, with Buller being parodied as "Judge Thumb".[4][6]

Several court rulings in the 19th-century United States referred to a supposed common-law doctrine that allowed wife beating with an implement smaller than a thumb.[4][9] In an 1824 case in Mississippi, the judge ruled, citing Blackstone's commentary, that a man could enforce "discipline" upon his wife by using a whip or stick no wider than his (the judge's) thumb.[6][9] In an 1874 case in North Carolina, the judge ruled, "We assume that the old doctrine that a husband had the right to whip his wife, provided that he used a switch no larger than his thumb, is not the law in North Carolina".[6][9]

The connection between wife beating and the phrase rule of thumb was first made in 1976, in a report on domestic violence by women's-rights advocate Del Martin.[4][9] Martin, erroneously citing the thumb-size standard as fact, wrote:

For instance, the common-law doctrine had been modified to allow the husband 'the right to whip his wife, provided that he used a switch no bigger than his thumb'—a rule of thumb, so to speak.[9]

While Martin appears to have meant the phrase rule of thumb only as a figure of speech, some feminist writers treated it as a literal reference to an earlier law.[4][9] The following year, a book on battered women stated:

One of the reasons nineteenth century British wives were dealt with so harshly by their husbands and by their legal system was the 'rule of thumb' [...] In other words, wifebeating was legal.[6]

This book was cited in a number of law journals affirming the spurious legal doctrine of the "rule of thumb".[6][8] In 1982, the United States Commission on Civil Rights issued a report on domestic abuse titled "Under the Rule of Thumb", citing the same volume.[8] However, the contributor in question, journalist Terry Davidson, never stated that the alleged law was the origin of the phrase itself.[6]

See also


  1. ^ Whether Buller was supposed to have meant his own thumb or the husband's is unknown.[6][8]


  1. ^ a b Brewer, Ebenezer Cobham (2001). The Wordsworth Dictionary of Phrase and Fable. Ware, UK: Wordsworth Editions. p. 1076. ISBN 1-84-022310-3. 
  2. ^ a b "rule of thumb, n. and adj.". OED Online. September 2016. Oxford University Press. Retrieved 25 October 2016
  3. ^ a b Martin, Gary. "'Rule of thumb' – the meaning and origin of this phrase". 
  4. ^ a b c d e f g O'Conner, Patricia T.; Kellerman, Stewart (2009). Origins of the Specious: Myths and Misconceptions of the English Language. Random House. pp. 123–126. ISBN 978-1-58-836856-0. 
  5. ^ a b c Safire, William (2003). No Uncertain Terms: More Writing from the Popular "On Language" Column in The New York Times Magazine. Simon and Schuster. pp. 188–90. ISBN 978-0-74-324955-3. 
  6. ^ a b c d e f g h i j k Kelly, Henry Ansgar (September 1994). "Rule of Thumb and the Folklaw of the Husband's Stick" (PDF). Journal of Legal Education. 44 (3): 341–65. JSTOR 42893341. 
  7. ^ Kelly, James (1721) [reprinted 1977]. A complete collection of Scotish proverbs explained and made intelligible to the English reader. Norwood, Pa.: Norwood Editions. p. 257. ISBN 978-0-84-821450-0. 
  8. ^ a b c d e Clapp, James E.; Thornburg, Elizabeth G.; Galanter, Marc; Shapiro, Fred R. (2011). Lawtalk: the unknown stories behind familiar legal expressions. Yale University Press. pp. 219–. ISBN 0-30-017817-4. 
  9. ^ a b c d e f g Wilton, David (2008). Word Myths: Debunking Linguistic Urban Legends. Oxford University Press. ISBN 978-0-19-974083-3. 
  10. ^ Foyster, Elizabeth (2005). Marital violence : an English family history, 1660–1857 (1st ed.). New York: Cambridge University Press. p. 12. ISBN 0521834511. 

Further reading

  • Calvert, Robert (1974). "Criminal and Civil Liability in Husband-Wife Assaults". In Steinmetz, S.K.; Straus, M.A. Violence in the Family. New York: Harper and Row. 
  • Freyd, Jennifer; Johnson, J.Q. (1998). "Commentary: Domestic Violence, Folk Etymologies, & 'Rule of Thumb'". University of Oregon. 
  • "Under the Rule of Thumb: Battered Women and the Administration of Justice" (PDF). Washington, D.C.: United States Commission on Civil Rights. January 1982. 

External links

  • "Does 'rule of thumb' refer to an old law permitting wife beating?" The Straight Dope
  • "Rule of thumb" World Wide Words
  • "North Carolina – Violence women, European Men Profeminist Network": Discussion of spurious legal "rule of thumb"
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