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Metamath Proof Explorer
Theorem olc
Description: Introduction of a disjunct. Axiom *1.3 of WhiteheadRussell p. 96.
(Contributed by NM, 30-Aug-1993)
|
|
Ref |
Expression |
|
Assertion |
olc |
⊢ ( 𝜑 → ( 𝜓 ∨ 𝜑 ) ) |
Proof
| Step |
Hyp |
Ref |
Expression |
| 1 |
|
ax-1 |
⊢ ( 𝜑 → ( ¬ 𝜓 → 𝜑 ) ) |
| 2 |
1
|
orrd |
⊢ ( 𝜑 → ( 𝜓 ∨ 𝜑 ) ) |