Theorem eal ≪ | index | src | ≫

theorem eal {x: nat} (a: wff x): $ A. x a -> a $;

Step	Hyp	Ref	Expression
1		ax_3	(~a -> ~A. x a) -> A. x a -> a
2		exnal	E. x ~a <-> ~A. x a
3		iex	~a -> E. x ~a
4	2, 3	sylib	~a -> ~A. x a
5	1, 4	ax_mp	A. x a -> a

Axiom use

axs_prop_calc (ax_1, ax_2, ax_3, ax_mp), axs_pred_calc (ax_gen, ax_4, ax_5, ax_6, ax_7, ax_12)