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Theorem ax11o 1761
 Description: Derivation of set.mm's original ax-11o 1762 from the shorter ax-11 1452 that has replaced it. An open problem is whether this theorem can be proved without relying on ax-16 1753 or ax-17 1474. Normally, ax11o 1761 should be used rather than ax-11o 1762, except by theorems specifically studying the latter's properties. (Contributed by NM, 3-Feb-2007.)
Assertion
Ref Expression
ax11o (¬ ∀𝑥 𝑥 = 𝑦 → (𝑥 = 𝑦 → (𝜑 → ∀𝑥(𝑥 = 𝑦𝜑))))

Proof of Theorem ax11o
Dummy variable 𝑧 is distinct from all other variables.
StepHypRef Expression
1 ax-11 1452 . 2 (𝑥 = 𝑧 → (∀𝑧𝜑 → ∀𝑥(𝑥 = 𝑧𝜑)))
21ax11a2 1760 1 (¬ ∀𝑥 𝑥 = 𝑦 → (𝑥 = 𝑦 → (𝜑 → ∀𝑥(𝑥 = 𝑦𝜑))))
 Colors of variables: wff set class Syntax hints:  ¬ wn 3   → wi 4  ∀wal 1297 This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 105  ax-ia2 106  ax-ia3 107  ax-in2 585  ax-io 671  ax-5 1391  ax-7 1392  ax-gen 1393  ax-ie1 1437  ax-ie2 1438  ax-8 1450  ax-10 1451  ax-11 1452  ax-i12 1453  ax-4 1455  ax-17 1474  ax-i9 1478  ax-ial 1482 This theorem depends on definitions:  df-bi 116  df-nf 1405  df-sb 1704 This theorem is referenced by:  ax11b  1765  equs5  1768
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