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The letter ℘: name and origin? (2017)

(mathoverflow.net)
283 points IdealeZahlen | 1 comments | 14 Nov 24 16:28 UTC | HN request time: 0.214s | source
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Symbiote ◴[14 Nov 24 19:50 UTC] No.42140408[source]▶
In the same Unicode block is "2129 ℩ TURNED GREEK SMALL LETTER IOTA" with explanation "unique element fulfilling a description (logic)".

That seems a ridiculous choice for a symbol — turning one of the most symmetrical letters upside down!

Background: https://philosophy.stackexchange.com/questions/51563/what-is...

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Archelaos ◴[14 Nov 24 20:37 UTC] No.42140934[source]▶
It could be motivated by the fact that Russell and Whitehead needed a symbol for printing that the printer had in his type case but could not be confused with anything else. Taking a iota and simply turning it upside down would then be a rather ingenious idea. But that is just my speculation ...
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eesmith ◴[14 Nov 24 21:21 UTC] No.42141354[source]▶
https://math.stackexchange.com/questions/1885938/whats-meani... says 'in the article Frege, Peano and Russell on Descriptions: a Comparison, Francisco A. Rodríguez-Consuegra tracks down the source to Peano's Studii di logica matematica (1897) as where the operator first appears'

That page in 'Studii di logica matematica' appears to be https://archive.org/details/peano-studii-di-logica-matematic... .

It also uses an upside-down C and upside-down E.

replies(1): >>42142600 #
1. Archelaos ◴[14 Nov 24 23:54 UTC] No.42142600[source]▶
And the Lambda looks like an upside-down V. The bases of all these upside-down letters do not match the baseline of the text. Obviously there were no special upside-down moveable types available of freshly cast for this book. Peano had to creatively repurpose what types were available.