Theorem pm2.5dc 868

Description: Negating an implication for a decidable antecedent. Theorem *2.5 of [WhiteheadRussell] p. 107 under a decidability condition. (Contributed by Jim Kingdon, 29-Mar-2018.)

Assertion

Ref	Expression
pm2.5dc	|- (DECID ph -> ( -. ( ph -> ps ) -> ( -. ph -> ps ) ) )

Proof of Theorem pm2.5dc

Step	Hyp	Ref	Expression
1		pm2.5gdc 867	1 |- (DECID ph -> ( -. ( ph -> ps ) -> ( -. ph -> ps ) ) )

Syntax hints:   -. wn 3   -> wi 4  DECID wdc 835

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-in1 615  ax-in2 616  ax-io 710

This theorem depends on definitions:  df-bi 117  df-stab 832  df-dc 836

This theorem is referenced by:  pm5.11dc  910