Metamath Proof Explorer

Theorem frege26

Description: Identical to idd . Proposition 26 of Frege1879 p. 42. (Contributed by RP, 24-Dec-2019) (Proof modification is discouraged.)

Ref Expression
Assertion frege26 
|- ( ph -> ( ps -> ps ) )

Proof

Step Hyp Ref Expression
1 ax-frege1 
 |-  ( ps -> ( ph -> ps ) )
2 ax-frege8 
 |-  ( ( ps -> ( ph -> ps ) ) -> ( ph -> ( ps -> ps ) ) )
3 1 2 ax-mp 
 |-  ( ph -> ( ps -> ps ) )