Metamath Proof Explorer

Theorem iba

Description: Introduction of antecedent as conjunct. Theorem *4.73 of WhiteheadRussell p. 121. (Contributed by NM, 30-Mar-1994)

Ref Expression
Assertion iba φ ψ ψ φ


Step Hyp Ref Expression
1 pm3.21 φ ψ ψ φ
2 simpl ψ φ ψ
3 1 2 impbid1 φ ψ ψ φ