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Theorem pm2.01 171
Description: Reductio ad absurdum. Theorem *2.01 of [WhiteheadRussell] p. 100. Also called the weak Clavius law, and provable in minimal calculus, contrary to the Clavius law pm2.18 113. (Contributed by NM, 18-Aug-1993.) (Proof shortened by Mel L. 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 22 . 2  |-  ( -. 
ph  ->  -.  ph )
21, 1ja 164 1  |-  ( (
ph  ->  -.  ph )  ->  -.  ph )
Colors of variables: wff setvar class
Syntax hints:   -. wn 3    -> wi 4
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8
This theorem is referenced by:  bijust  186  pm4.8  366  axin1  2396  dtrucor2  4598  ominf  7737  elirr  8066  hfninf  30902  bj-pm2.01i  31086  bj-nimn  31087  bj-dtrucor2v  31327
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