This is an inofficial mirror of http://metamath.tirix.org for personal testing of a visualizer extension only.
Metamath Proof Explorer
Description: Theorem *2.68 of WhiteheadRussell p. 108. (Contributed by NM, 3-Jan-2005)
|
|
Ref |
Expression |
|
Assertion |
pm2.68 |
⊢ ( ( ( 𝜑 → 𝜓 ) → 𝜓 ) → ( 𝜑 ∨ 𝜓 ) ) |
Proof
| Step |
Hyp |
Ref |
Expression |
| 1 |
|
jarl |
⊢ ( ( ( 𝜑 → 𝜓 ) → 𝜓 ) → ( ¬ 𝜑 → 𝜓 ) ) |
| 2 |
1
|
orrd |
⊢ ( ( ( 𝜑 → 𝜓 ) → 𝜓 ) → ( 𝜑 ∨ 𝜓 ) ) |