Theorem axc7 2323

Description: Show that the original axiom ax-c7 39255 can be derived from ax-10 2147 (hbn1 2148), sp 2191 and propositional calculus. See ax10fromc7 39265 for the rederivation of ax-10 2147 from ax-c7 39255.

Normally, axc7 2323 should be used rather than ax-c7 39255, except by theorems specifically studying the latter's properties. (Contributed by NM, 21-May-2008.)

Assertion

Ref	Expression
axc7	⊢ (¬ ∀𝑥 ¬ ∀𝑥𝜑 → 𝜑)

Proof of Theorem axc7

Step	Hyp	Ref	Expression
1		sp 2191	. 2 ⊢ (∀𝑥𝜑 → 𝜑)
2		hbn1 2148	. 2 ⊢ (¬ ∀𝑥𝜑 → ∀𝑥 ¬ ∀𝑥𝜑)
3	1, 2	nsyl4 158	1 ⊢ (¬ ∀𝑥 ¬ ∀𝑥𝜑 → 𝜑)

Syntax hints:  ¬ wn 3   → wi 4  ∀wal 1540

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1797  ax-4 1811  ax-5 1912  ax-6 1969  ax-7 2010  ax-10 2147  ax-12 2185

This theorem depends on definitions:  df-bi 207  df-ex 1782

This theorem is referenced by:  modal-b  2325  axc10  2390  hbntg  36016  bj-modalb  36955  bj-axc10v  37035  axc5c4c711  44751  hbntal  44903