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Theorem pm2.01 158
Description: Reductio ad absurdum. Theorem *2.01 of [WhiteheadRussell] p. 100. (Contributed by NM, 18-Aug-1993.) (Proof shortened by O'Cat, 21-Nov-2008.) (Proof shortened by Wolf Lammen, 31-Oct-2012.)
Assertion
Ref Expression
pm2.01  |-  ( (
ph  ->  -.  ph )  ->  -.  ph )

Proof of Theorem pm2.01
StepHypRef Expression
1 id 19 . 2  |-  ( -. 
ph  ->  -.  ph )
21, 1ja 151 1  |-  ( (
ph  ->  -.  ph )  ->  -.  ph )
Colors of variables: wff set class
Syntax hints:   -. wn 3    -> wi 4
This theorem is referenced by:  bijust  173  pm4.8  352  dtrucor2  3770  ominf  6564  elirr  6801
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-3 7  ax-mp 8
Copyright terms: Public domain