Metamath Proof Explorer

Theorem orri

Description: Infer disjunction from implication. (Contributed by NM, 11-Jun-1994)

Ref Expression
Hypothesis orri.1 
|- ( -. ph -> ps )
Assertion orri 
|- ( ph \/ ps )

Proof

Step Hyp Ref Expression
1 orri.1 
 |-  ( -. ph -> ps )
2 df-or 
 |-  ( ( ph \/ ps ) <-> ( -. ph -> ps ) )
3 1 2 mpbir 
 |-  ( ph \/ ps )