Q: I was reading Shoot the Lawyer Twice, a mystery novel by Michael Bowen, and noticed the term “Lesbian rule.” It was said to be a flexible ruler used to measure curves. Can you tell me more about the term?
A: The Oxford English Dictionary describes a “Lesbian rule” as “a mason’s rule made of lead, which could be bent to fit the curves of a moulding.” It traces the term back to Aristotle’s Nicomachean Ethics.
In the 17th century, according to the OED, the phrase was commonly used in English in a figurative sense, referring to “a principle of judgement that is pliant and accommodating.”
In fact, the first known English use of “Lesbian” in this sense was figurative. The poet Samuel Daniel, in his “Epistle to Sir Thomas Egerton” (1601), writes that justice requires the law to be applied flexibly, like a “Lesbian square” that “Plies to the worke, not forc’th the worke to it.”
But what does the word “Lesbian” have to do with an instrument for measuring curves?
A pliable mason’s rule, it turns out, was made of a kind of lead, found on the island of Lesbos, that was flexible enough to be shaped to fit a curved edge.
In the passage from the Nicomachean Ethics mentioned in the OED, Aristotle uses the Lesbian rule both literally and figuratively:
“For when the thing is indefinite the rule also is indefinite, like the leaden rule used in making the Lesbian moulding; the rule adapts itself to the shape of the stone and is not rigid, and so too the decree is adapted to the facts.”