Description: Contraposition. Theorem *2.03 of WhiteheadRussell p. 100. (Contributed by NM, 29-Dec-1992) (Proof shortened by Wolf Lammen, 12-Feb-2013)
Ref | Expression | ||
---|---|---|---|
Assertion | con2 | ⊢ ( ( 𝜑 → ¬ 𝜓 ) → ( 𝜓 → ¬ 𝜑 ) ) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | id | ⊢ ( ( 𝜑 → ¬ 𝜓 ) → ( 𝜑 → ¬ 𝜓 ) ) | |
2 | 1 | con2d | ⊢ ( ( 𝜑 → ¬ 𝜓 ) → ( 𝜓 → ¬ 𝜑 ) ) |