Theorem frege18 43251

Description: Closed form of a syllogism followed by a swap of antecedents. Proposition 18 of [Frege1879] p. 39. (Contributed by RP, 24-Dec-2019.) (Proof modification is discouraged.)

Assertion

Ref	Expression
frege18	⊢ ((𝜑 → (𝜓 → 𝜒)) → ((𝜃 → 𝜑) → (𝜓 → (𝜃 → 𝜒))))

Proof of Theorem frege18

Step	Hyp	Ref	Expression
1		frege5 43233	. 2 ⊢ ((𝜑 → (𝜓 → 𝜒)) → ((𝜃 → 𝜑) → (𝜃 → (𝜓 → 𝜒))))
2		frege16 43249	. 2 ⊢ (((𝜑 → (𝜓 → 𝜒)) → ((𝜃 → 𝜑) → (𝜃 → (𝜓 → 𝜒)))) → ((𝜑 → (𝜓 → 𝜒)) → ((𝜃 → 𝜑) → (𝜓 → (𝜃 → 𝜒)))))
3	1, 2	ax-mp 5	1 ⊢ ((𝜑 → (𝜓 → 𝜒)) → ((𝜃 → 𝜑) → (𝜓 → (𝜃 → 𝜒))))

Syntax hints:   → wi 4

This theorem was proved from axioms:  ax-mp 5  ax-frege1 43223  ax-frege2 43224  ax-frege8 43242

This theorem is referenced by:  frege19  43257  frege23  43258  frege20  43261  frege51  43288  frege64a  43315  frege64b  43342  frege64c  43360  frege82  43378