Metamath Proof Explorer

Theorem pm5.4

Description: Antecedent absorption implication. Theorem *5.4 of WhiteheadRussell p. 125. (Contributed by NM, 5-Aug-1993)

Ref Expression
Assertion pm5.4 
|- ( ( ph -> ( ph -> ps ) ) <-> ( ph -> ps ) )

Proof

Step Hyp Ref Expression
1 pm5.5 
 |-  ( ph -> ( ( ph -> ps ) <-> ps ) )
2 1 pm5.74i 
 |-  ( ( ph -> ( ph -> ps ) ) <-> ( ph -> ps ) )