Axiom ax-5 952

Description: Axiom of Quantified Implication. This axiom moves a quantifier from outside to inside an implication, quantifying ps. Notice that x must not be a free variable in the antecedent of the quantified implication, and we express this by binding ph to "protect" the axiom from a ph containing a free x. One of the 4 axioms of pure predicate calculus. Axiom scheme C4' in [Megill] p. 448 (p. 16 of the preprint). It is a special case of Lemma 5 of [Monk2] p. 108 and Axiom 5 of [Mendelson] p. 69.

Assertion

Ref	Expression
ax-5	|- (A.x(A.xph -> ps) -> (A.xph -> A.xps))

Detailed syntax breakdown of Axiom ax-5

Step	Hyp	Ref	Expression
1		wph	. . . . 5 wff ph
2		vx	. . . . 5 set x
3	1, 2	wal 950	. . . 4 wff A.xph
4		wps	. . . 4 wff ps
5	3, 4	wi 3	. . 3 wff (A.xph -> ps)
6	5, 2	wal 950	. 2 wff A.x(A.xph -> ps)
7	4, 2	wal 950	. . 3 wff A.xps
8	3, 7	wi 3	. 2 wff (A.xph -> A.xps)
9	6, 8	wi 3	1 wff (A.x(A.xph -> ps) -> (A.xph -> A.xps))

This axiom is referenced by:  a5i 965  19.20 970

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