Metamath Proof Explorer

Theorem pm2.86

Description: Converse of axiom ax-2 . Theorem *2.86 of WhiteheadRussell p. 108. (Contributed by NM, 25-Apr-1994) (Proof shortened by Wolf Lammen, 3-Apr-2013)

Ref Expression
Assertion pm2.86 φ ψ φ χ φ ψ χ


Step Hyp Ref Expression
1 id φ ψ φ χ φ ψ φ χ
2 1 pm2.86d φ ψ φ χ φ ψ χ