MPE Home Metamath Proof Explorer < Previous   Next >
Nearby theorems
Mirrors  >  Home  >  MPE Home  >  Th. List  >  axextnd Structured version   Visualization version   GIF version

Theorem axextnd 9451
Description: A version of the Axiom of Extensionality with no distinct variable conditions. (Contributed by NM, 14-Aug-2003.)
Assertion
Ref Expression
axextnd 𝑥((𝑥𝑦𝑥𝑧) → 𝑦 = 𝑧)

Proof of Theorem axextnd
Dummy variable 𝑤 is distinct from all other variables.
StepHypRef Expression
1 nfnae 2351 . . . . . . . 8 𝑥 ¬ ∀𝑥 𝑥 = 𝑦
2 nfnae 2351 . . . . . . . 8 𝑥 ¬ ∀𝑥 𝑥 = 𝑧
31, 2nfan 1868 . . . . . . 7 𝑥(¬ ∀𝑥 𝑥 = 𝑦 ∧ ¬ ∀𝑥 𝑥 = 𝑧)
4 nfcvf 2817 . . . . . . . . . 10 (¬ ∀𝑥 𝑥 = 𝑦𝑥𝑦)
54adantr 480 . . . . . . . . 9 ((¬ ∀𝑥 𝑥 = 𝑦 ∧ ¬ ∀𝑥 𝑥 = 𝑧) → 𝑥𝑦)
65nfcrd 2800 . . . . . . . 8 ((¬ ∀𝑥 𝑥 = 𝑦 ∧ ¬ ∀𝑥 𝑥 = 𝑧) → Ⅎ𝑥 𝑤𝑦)
7 nfcvf 2817 . . . . . . . . . 10 (¬ ∀𝑥 𝑥 = 𝑧𝑥𝑧)
87adantl 481 . . . . . . . . 9 ((¬ ∀𝑥 𝑥 = 𝑦 ∧ ¬ ∀𝑥 𝑥 = 𝑧) → 𝑥𝑧)
98nfcrd 2800 . . . . . . . 8 ((¬ ∀𝑥 𝑥 = 𝑦 ∧ ¬ ∀𝑥 𝑥 = 𝑧) → Ⅎ𝑥 𝑤𝑧)
106, 9nfbid 1872 . . . . . . 7 ((¬ ∀𝑥 𝑥 = 𝑦 ∧ ¬ ∀𝑥 𝑥 = 𝑧) → Ⅎ𝑥(𝑤𝑦𝑤𝑧))
11 elequ1 2037 . . . . . . . . 9 (𝑤 = 𝑥 → (𝑤𝑦𝑥𝑦))
12 elequ1 2037 . . . . . . . . 9 (𝑤 = 𝑥 → (𝑤𝑧𝑥𝑧))
1311, 12bibi12d 334 . . . . . . . 8 (𝑤 = 𝑥 → ((𝑤𝑦𝑤𝑧) ↔ (𝑥𝑦𝑥𝑧)))
1413a1i 11 . . . . . . 7 ((¬ ∀𝑥 𝑥 = 𝑦 ∧ ¬ ∀𝑥 𝑥 = 𝑧) → (𝑤 = 𝑥 → ((𝑤𝑦𝑤𝑧) ↔ (𝑥𝑦𝑥𝑧))))
153, 10, 14cbvald 2313 . . . . . 6 ((¬ ∀𝑥 𝑥 = 𝑦 ∧ ¬ ∀𝑥 𝑥 = 𝑧) → (∀𝑤(𝑤𝑦𝑤𝑧) ↔ ∀𝑥(𝑥𝑦𝑥𝑧)))
16 axext3 2633 . . . . . 6 (∀𝑤(𝑤𝑦𝑤𝑧) → 𝑦 = 𝑧)
1715, 16syl6bir 244 . . . . 5 ((¬ ∀𝑥 𝑥 = 𝑦 ∧ ¬ ∀𝑥 𝑥 = 𝑧) → (∀𝑥(𝑥𝑦𝑥𝑧) → 𝑦 = 𝑧))
18 19.8a 2090 . . . . 5 (𝑦 = 𝑧 → ∃𝑥 𝑦 = 𝑧)
1917, 18syl6 35 . . . 4 ((¬ ∀𝑥 𝑥 = 𝑦 ∧ ¬ ∀𝑥 𝑥 = 𝑧) → (∀𝑥(𝑥𝑦𝑥𝑧) → ∃𝑥 𝑦 = 𝑧))
2019ex 449 . . 3 (¬ ∀𝑥 𝑥 = 𝑦 → (¬ ∀𝑥 𝑥 = 𝑧 → (∀𝑥(𝑥𝑦𝑥𝑧) → ∃𝑥 𝑦 = 𝑧)))
21 ax6e 2286 . . . . 5 𝑥 𝑥 = 𝑧
22 ax7 1989 . . . . . 6 (𝑥 = 𝑦 → (𝑥 = 𝑧𝑦 = 𝑧))
2322aleximi 1799 . . . . 5 (∀𝑥 𝑥 = 𝑦 → (∃𝑥 𝑥 = 𝑧 → ∃𝑥 𝑦 = 𝑧))
2421, 23mpi 20 . . . 4 (∀𝑥 𝑥 = 𝑦 → ∃𝑥 𝑦 = 𝑧)
2524a1d 25 . . 3 (∀𝑥 𝑥 = 𝑦 → (∀𝑥(𝑥𝑦𝑥𝑧) → ∃𝑥 𝑦 = 𝑧))
26 ax6e 2286 . . . . 5 𝑥 𝑥 = 𝑦
27 ax7 1989 . . . . . . 7 (𝑥 = 𝑧 → (𝑥 = 𝑦𝑧 = 𝑦))
28 equcomi 1990 . . . . . . 7 (𝑧 = 𝑦𝑦 = 𝑧)
2927, 28syl6 35 . . . . . 6 (𝑥 = 𝑧 → (𝑥 = 𝑦𝑦 = 𝑧))
3029aleximi 1799 . . . . 5 (∀𝑥 𝑥 = 𝑧 → (∃𝑥 𝑥 = 𝑦 → ∃𝑥 𝑦 = 𝑧))
3126, 30mpi 20 . . . 4 (∀𝑥 𝑥 = 𝑧 → ∃𝑥 𝑦 = 𝑧)
3231a1d 25 . . 3 (∀𝑥 𝑥 = 𝑧 → (∀𝑥(𝑥𝑦𝑥𝑧) → ∃𝑥 𝑦 = 𝑧))
3320, 25, 32pm2.61ii 177 . 2 (∀𝑥(𝑥𝑦𝑥𝑧) → ∃𝑥 𝑦 = 𝑧)
343319.35ri 1847 1 𝑥((𝑥𝑦𝑥𝑧) → 𝑦 = 𝑧)
Colors of variables: wff setvar class
Syntax hints:  ¬ wn 3  wi 4  wb 196  wa 383  wal 1521  wex 1744  wnfc 2780
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1762  ax-4 1777  ax-5 1879  ax-6 1945  ax-7 1981  ax-8 2032  ax-9 2039  ax-10 2059  ax-11 2074  ax-12 2087  ax-13 2282  ax-ext 2631
This theorem depends on definitions:  df-bi 197  df-or 384  df-an 385  df-tru 1526  df-ex 1745  df-nf 1750  df-cleq 2644  df-clel 2647  df-nfc 2782
This theorem is referenced by:  zfcndext  9473  axextprim  31704  axextdfeq  31827  axextndbi  31834
  Copyright terms: Public domain W3C validator