----------

   y   z      xy   xz
   o   o       o   o
    \ /         \ /
     o           o
     |           |
    x@     =     @

 x((y)(z)) = ((xy)(xz))

-------------------------

Here is the proof of the Double Negation Theorem,
marked as "Reflection" or "Consequence 1" in LOF:

¤~~~~~~~~~¤~~~~~~~~~¤~~~DEQ~~~¤~~~~~~~~~¤~~~~~~~~~¤

     xo
       \
        o
         \
          @

===================== I2 [Unfold "(())"]

     xo       o
       \     /
        o   o
         \ /
          @

===