Description: The third of four axioms in the Russell-Bernays axiom system. (Contributed by Anthony Hart, 13-Aug-2011) (Proof modification is discouraged.) (New usage is discouraged.)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | rb-ax3 | |- ( -. ph \/ ( ps \/ ph ) ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | pm2.46 | |- ( -. ( ps \/ ph ) -> -. ph ) |
|
| 2 | 1 | con1i | |- ( -. -. ph -> ( ps \/ ph ) ) |
| 3 | 2 | orri | |- ( -. ph \/ ( ps \/ ph ) ) |