Metamath Proof Explorer


Theorem bj-imim21

Description: The propositional function ( ph -> ( . -> ps ) ) is decreasing. (Contributed by BJ, 19-Jul-2019)

Ref Expression
Assertion bj-imim21 ( ( 𝜑 → 𝜓 ) → ( ( 𝜒 → ( 𝜓 → 𝜃 ) ) → ( 𝜒 → ( 𝜑 → 𝜃 ) ) ) )

Proof

Step Hyp Ref Expression
1 imim1 ⊢ ( ( 𝜑 → 𝜓 ) → ( ( 𝜓 → 𝜃 ) → ( 𝜑 → 𝜃 ) ) )
2 1 imim2d ⊢ ( ( 𝜑 → 𝜓 ) → ( ( 𝜒 → ( 𝜓 → 𝜃 ) ) → ( 𝜒 → ( 𝜑 → 𝜃 ) ) ) )