[FOM] The very bearable EFQ

[Martin Davis]

A very brief comment: Suppose one knows that A and ~B are true and wishes
to prove C.  A reductio ad absurdam proof might proceed by proving B from A
and ~C. The principle involved can be rendered:

                                 if A,~C |- B, then A,~B |- C

Then the special case B=A gives

                                           A,~A |- C

This shows that to eliminate EFQ one must interdict a simple special case
of an important general logical principle.

Martin
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