Metamath Proof Explorer


Theorem frege17

Description: A closed form of com3l . Proposition 17 of Frege1879 p. 39. (Contributed by RP, 24-Dec-2019) (Proof modification is discouraged.)

Ref Expression
Assertion frege17 φ ψ χ θ ψ χ φ θ

Proof

Step Hyp Ref Expression
1 ax-frege8 φ ψ χ θ ψ φ χ θ
2 frege16 φ ψ χ θ ψ φ χ θ φ ψ χ θ ψ χ φ θ
3 1 2 ax-mp φ ψ χ θ ψ χ φ θ