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Axiom ax-10 1966
Description: Axiom of Quantified Negation. Axiom C5-2 of [Monk2] p. 113. This axiom scheme is logically redundant (see ax10w 1954) but is used as an auxiliary axiom scheme to achieve scheme completeness. It means that 𝑥 is not free in ¬ ∀𝑥𝜑. (Contributed by NM, 21-May-2008.) Use its alias hbn1 1967 instead if you must use it. Any theorem in first order logic (FOL) that contains only set variables that are all mutually distinct, and has no wff variables, can be proved *without* using ax-10 1966 through ax-13 2137, by invoking ax10w 1954 through ax13w 1961. We encourage proving theorems *without* ax-10 1966 through ax-13 2137 and moving them up to the ax-4 1713 through ax-9 1947 section. (New usage is discouraged.)
Assertion
Ref Expression
ax-10 (¬ ∀𝑥𝜑 → ∀𝑥 ¬ ∀𝑥𝜑)

Detailed syntax breakdown of Axiom ax-10
StepHypRef Expression
1 wph . . . 4 wff 𝜑
2 vx . . . 4 setvar 𝑥
31, 2wal 1472 . . 3 wff 𝑥𝜑
43wn 3 . 2 wff ¬ ∀𝑥𝜑
54, 2wal 1472 . 2 wff 𝑥 ¬ ∀𝑥𝜑
64, 5wi 4 1 wff (¬ ∀𝑥𝜑 → ∀𝑥 ¬ ∀𝑥𝜑)
Colors of variables: wff setvar class
This axiom is referenced by:  hbn1  1967
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