Simanaitis Says

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I RECENTLY posted a Facebook comment mentioning “rule of thumb” as contrasted with more scientific methods of measurement. Think crowd size, for instance. Before doing so, I felt compelled to research the term to avoid going off half-cocked (and there’s another phrase worth a look one day).

Darned if rule of thumb doesn’t have an interesting linguistic history.

My old pals Merriam and Webster Online give two definitions: “a method or procedure based on experience and common sense” and “a general principle regarded as roughly correct, but not intended to be scientifically accurate.”

The Compact Edition of the Oxford English Dictionary, 1971, is a bit more forceful on the matter: “A method or procedure derived entirely from practice or experience, without any basis in scientific knowledge; a roughly practical method.”

The OED’s first reference dates from Sir William Hope’s treatise Fencing-Master, 1692: “What he doth, he doth by rule of Thumb, and not by Art.”

English is not alone with the term. Italian has regola de pollice: rule of thumb, directly. The Hebrew כלל אצבע is a “rule of the finger.” The Persian قاعده سرانگشتی translates into “a finger tip’s rule.”

Measurement of digits is prominent in rule of thumb’s origin, what with the length of one’s first thumb joint being approximately an inch. Indeed, the Dutch word duim means both “thumb” and “inch.”

Alas, there’s a threatening association with the term too: the maximum thickness of a stick with which it was permissible for a man to beat his wife. Sometime prior to Charles II, who reigned from 1660 to 1685, English common law permitted a husband’s “moderate correction” of his spouse, though beating per se was specifically excluded.

Nonetheless, in 1782 English satirist James Gillray published Judge Thumb, a cartoon taking English judge Sir Francis Butler to task for allegedly suggesting the rule of thumb.


Judge Thumb. or Patent Sticks for Family Correction: Warranted Lawful!, by James Gillray, 1782.

In his cartoon, Gillray offered the following dialogue: Judge Thumb says, “Who wants a cure for a nasty Wife? Here’s your nice Family Amusement for Winter Evenings! Who buys here?” The woman says, “Help! Murder, for God’s Sake, Murder!” The man responds, “Murder, hey? it’s the Law, you Bitch: it’s not bigger than my Thumb.”

Imagine such talk today!

In any case, accuracy of a rule of thumb would seem to depend on the size of the thumb doing the ruling. ds

© Dennis Simanaitis,, 2017

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