[lit-ideas] Re: Pons Asinorum

  • From: Jlsperanza@xxxxxxx
  • To: lit-ideas@xxxxxxxxxxxxx
  • Date: Wed, 10 Jun 2009 10:30:39 EDT



"Peregrine..began to read Euclid..but he had scarce advanced beyond the 
Pons Asinorum, when his ardor abated."
     Smollett

  "He never crossed the bridge of asses"


  Suppose the name of our ass is "Mike"



                  MIKE

                    .
                   .
                    .
                    . - - - - - - - - - - - ->  fodder

"Mike" reasons, "Surely it's shorter to use the hypothenuse". He learned
all that in a barn.



In a message dated 6/10/2009 10:02:39 A.M. Eastern Daylight Time,
karltrogge@xxxxxxxx writes:
I would be very interested in hearing from Mr  Speranza an explication
of this famous proof, which seems to have been  left out of my education!
In German, the term ESELSBRÜCKE seems not to share  this curious
etymology (which makes no reference whatsoever to a  bridge).  And the
term 'Pons Asinorum' as I have learned it is  applied in Euclidean
geometry at some other point than this proof of  the shortness of
straight lines joining points (but as that seems to  be strangely
lacking in my education, perhaps this was left out as  well).  Could Mr 
Speranza please show us the sources for this  interesting account?


----

Sure. Actually, I learned it from M. Zeleny, recently. In a post to the 
forum CHORA, he was talking 'pons asinorum'. I replied publicly that according
 to the OED there is some dispute about the origin.

Let me see if I can retrieve M. Zeleny's interesting post from the CHORA
archives:

----

Zeleny is using Proclus:


         [Proclus] further relateed  that the Epicureans
         used to ridicule this  theorem as being evident even
         to an ass and requiring no  proof. They claimed that
         the theorem was "known"  (gnorimon) even to an ass
         that can invariably be  seen choosing to walk towards
         his fodder in a straight  line, in lieu of traversing the
         two sides of the triangle  formed by an outlying point.


Suppose I call this Ass, "Mike":



MIKE       . . . . . . . . . . . .  >   fodder



On the other hand, an Euclidean "Mike" would go triangular:



     MIKE

     .
     .
     .
     .
     .
     . . . - - - - - - - - - - - - ->  fodder.

Geary explains, "It's the mystique of the hypothenuse".

---

Zeleny continues:


           In his response,  Proclus pointed out that
           perceiving the  truth of the theorem is at a far remove
           from  understanding its proof as a reason why it is true.
           His focus on  proof remained at the foundation of
           geometrical  knowledge.  . . .

          The mediaeval  tutors, frustrated by the resistance of
           their charges  to the idea of a geometrical figure being
          congruent with its  own mirror image, paid an homage to
           Epicurus by  deeming this proposition the
           pons  asinorum, the bridge of asses.

Cheers,

J. L. Speranza
   Buenos Aires, Argentina
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