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Metamath Proof Explorer
Theorem orc
Description: Introduction of a disjunct. Theorem *2.2 of WhiteheadRussell p. 104.
(Contributed by NM, 30-Aug-1993)
|
|
Ref |
Expression |
|
Assertion |
orc |
⊢ ( 𝜑 → ( 𝜑 ∨ 𝜓 ) ) |
Proof
| Step |
Hyp |
Ref |
Expression |
| 1 |
|
pm2.24 |
⊢ ( 𝜑 → ( ¬ 𝜑 → 𝜓 ) ) |
| 2 |
1
|
orrd |
⊢ ( 𝜑 → ( 𝜑 ∨ 𝜓 ) ) |