theorem ngen {x: nat} (a: wff x): $ ~a $ > $ ~E. x a $;
| Step | Hyp | Ref | Expression |
|---|
| 1 |
|
notnot1 |
A. x ~a -> ~~A. x ~a |
| 2 |
1 |
conv ex |
A. x ~a -> ~E. x a |
| 3 |
|
hyp h |
~a |
| 4 |
3 |
ax_gen |
A. x ~a |
| 5 |
2, 4 |
ax_mp |
~E. x a |
Axiom use
axs_prop_calc
(ax_1,
ax_2,
ax_3,
ax_mp),
axs_pred_calc
(ax_gen)