Upside down E was Re: Mathematical Symbols

[Laurence Horn]

At 9:42 PM -0600 2/19/03, Barbara Need wrote:
>>Sounds good.  The standard folk etymology (the one I'd always
>>accepted) for the upside-down E is that it designates "Exists", a
>>better translation than "Some" for the (appropriately named)
>>existential quantifier.  (I think of it as an upside-down rather than
>>backward E since only the former story provides a parallel with the
>>universal.)  And the upside-down A for the universal quantifier
>>stands for "All", as Jim notes.  The fact that the latter involves an
>>English word ("All") supports the idea that the former should as well
>>("Exists"), but evidently such is not the case.
>>
>>Larry
>
>My first thought was: wouldn't an upside down E be identical to a
>right-side up E? But then I thought, when you look at someone's
>writing "upside down" it is the reversed E, because the writing is
>also right to left FROM YOUR PERSPECTIVE. But when I turn something
>upside down, I usually only rotate on a horizontal axis, not also on
>the vertical one. Is this the usual sense of turn something upside
>down?
>
I don't know; this is too complicated for me.  I write a
right-side-up E on a piece of paper and I turn the paper upside down
and I get an existential quantifier, not the E that I started with.
(Works with computer monitors too.)  Don't know from perspectives and
axes, but that's how I do it.

L