Description: Proof of older axiom ax-c16 . (Contributed by NM, 8-Nov-2006) (Revised by NM, 22-Sep-2017)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | axc16 | |- ( A. x x = y -> ( ph -> A. x ph ) ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | axc16g | |- ( A. x x = y -> ( ph -> A. x ph ) ) |