Theorem pm2.521dc 859

Description: Theorem *2.521 of [WhiteheadRussell] p. 107, but with an additional decidability condition. Note that by replacing in proof pm2.52 646 with conax1k 644, we obtain a proof of the more general instance where the last occurrence of ph is replaced with any ch. (Contributed by Jim Kingdon, 5-May-2018.)

Assertion

Ref	Expression
pm2.521dc	|- (DECID ph -> ( -. ( ph -> ps ) -> ( ps -> ph ) ) )

Proof of Theorem pm2.521dc

Step	Hyp	Ref	Expression
1		pm2.521gdc 858	1 |- (DECID ph -> ( -. ( ph -> ps ) -> ( ps -> ph ) ) )

Syntax hints:   -. wn 3   -> wi 4  DECID wdc 824

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 105  ax-ia2 106  ax-ia3 107  ax-in1 604  ax-in2 605  ax-io 699

This theorem depends on definitions:  df-bi 116  df-stab 821  df-dc 825

This theorem is referenced by: (None)