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Metamath Proof Explorer
Description: A general instance of Theorem *2.521 of WhiteheadRussell p. 107.
(Contributed by BJ, 28-Oct-2023)
|
|
Ref |
Expression |
|
Assertion |
pm2.521g |
⊢ ( ¬ ( 𝜑 → 𝜓 ) → ( 𝜓 → 𝜒 ) ) |
Proof
| Step |
Hyp |
Ref |
Expression |
| 1 |
|
conax1 |
⊢ ( ¬ ( 𝜑 → 𝜓 ) → ¬ 𝜓 ) |
| 2 |
1
|
pm2.21d |
⊢ ( ¬ ( 𝜑 → 𝜓 ) → ( 𝜓 → 𝜒 ) ) |