Theorem absurd ≪ | index | src | ≫

theorem absurd (a b: wff): $ ~a -> a -> b $;

Step	Hyp	Ref	Expression
1		ax_1	~a -> ~b -> ~a
2	1	a3d	~a -> a -> b

Axiom use

axs_prop_calc (ax_1, ax_2, ax_3, ax_mp)