Editing Rule of thumb (section)

=== English common law ===
[[File:Judge Thumb.jpg|thumb|right|alt=Cartoon of Sir Francis Buller in judges' robes and powdered wig, carrying bundles of rods whose ends resemble thumbs; 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]]{{r|Brunvand}} relates the phrase to domestic violence via an alleged rule under English common law which permitted [[wife-beating]] provided that the implement used was a rod or stick no thicker than a man's thumb.{{r|Safire 2003}} Wife-beating has been officially outlawed in England and the United States for centuries, but enforcement of the law was inconsistent, and wife-beating did continue. However, a rule of thumb permitting wife-beating was never codified in law.{{r|Clapp|Wallace & Roberson|Wilton}}

English jurist [[William Blackstone]] wrote in the late 1700s in his ''[[Commentaries on the Laws of England]]'' that, by an "old law", a husband had formerly been justified in using "moderate correction" against his wife but was barred from inflicting serious violence; Blackstone did not mention either thumbs or sticks.{{r|Clapp|Kelly}} According to Blackstone, this custom was in doubt by the late 1600s, and a woman was allowed "security of the peace" against an abusive husband.{{r|Kelly}}{{efn|One of Blackstone's sources was jurist [[Sir Matthew Hale]] who ruled in 1674 that a husband may admonish his wife and confine her to the house but not beat her.{{r|Clapp}}}} Twentieth-century legal scholar [[William L. Prosser]] wrote that there was "probably no truth to the legend" that a husband was allowed to beat his wife "with a stick no thicker than his thumb".{{r|O'Conner|Wallace & Roberson}}

The association between the thumb and implements of domestic violence can be traced to 1782, when English judge [[Sir Francis Buller]] was ridiculed for purportedly stating that a husband could beat his wife, provided that he used a stick no wider than his thumb.{{efn|Whether Buller was supposed to have meant his own thumb or the husband's is unknown. One history states, "A witty countess is said to have sent the next day to require the measurements of his thumb, that she might know the extent of her husband's right".{{r|Clapp|Kelly}}}} There is no record of Buller making such a statement, but the rumor generated much satirical press, with Buller being mocked as "Judge Thumb" in published jokes and cartoons.{{r|Clapp|Kelly|Foyster}}

In the following century, several court rulings in the United States referred to a supposed common-law doctrine which the judges believed had once allowed wife-beating with an implement smaller than a thumb.{{r|O'Conner}}{{r|Wilton|pp=41–42}} None of these courts referred to such a doctrine as a rule of thumb or endorsed such a rule, but all permitted some degree of wife-beating so long as it did not result in serious injury.{{r|Clapp}}