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Theorem nnsucelsuc 6009
Description: Membership is inherited by successors. The reverse direction holds for all ordinals, as seen at onsucelsucr 4199, but the forward direction, for all ordinals, implies excluded middle as seen as onsucelsucexmid 4215. (Contributed by Jim Kingdon, 25-Aug-2019.)
Assertion
Ref Expression
nnsucelsuc (B 𝜔 → (A B ↔ suc A suc B))

Proof of Theorem nnsucelsuc
Dummy variables x y are mutually distinct and distinct from all other variables.
StepHypRef Expression
1 eleq2 2098 . . . 4 (x = ∅ → (A xA ∅))
2 suceq 4105 . . . . 5 (x = ∅ → suc x = suc ∅)
32eleq2d 2104 . . . 4 (x = ∅ → (suc A suc x ↔ suc A suc ∅))
41, 3imbi12d 223 . . 3 (x = ∅ → ((A x → suc A suc x) ↔ (A ∅ → suc A suc ∅)))
5 eleq2 2098 . . . 4 (x = y → (A xA y))
6 suceq 4105 . . . . 5 (x = y → suc x = suc y)
76eleq2d 2104 . . . 4 (x = y → (suc A suc x ↔ suc A suc y))
85, 7imbi12d 223 . . 3 (x = y → ((A x → suc A suc x) ↔ (A y → suc A suc y)))
9 eleq2 2098 . . . 4 (x = suc y → (A xA suc y))
10 suceq 4105 . . . . 5 (x = suc y → suc x = suc suc y)
1110eleq2d 2104 . . . 4 (x = suc y → (suc A suc x ↔ suc A suc suc y))
129, 11imbi12d 223 . . 3 (x = suc y → ((A x → suc A suc x) ↔ (A suc y → suc A suc suc y)))
13 eleq2 2098 . . . 4 (x = B → (A xA B))
14 suceq 4105 . . . . 5 (x = B → suc x = suc B)
1514eleq2d 2104 . . . 4 (x = B → (suc A suc x ↔ suc A suc B))
1613, 15imbi12d 223 . . 3 (x = B → ((A x → suc A suc x) ↔ (A B → suc A suc B)))
17 noel 3222 . . . 4 ¬ A
1817pm2.21i 574 . . 3 (A ∅ → suc A suc ∅)
19 elsuci 4106 . . . . . . . 8 (A suc y → (A y A = y))
2019adantl 262 . . . . . . 7 (((A y → suc A suc y) A suc y) → (A y A = y))
21 simpl 102 . . . . . . . 8 (((A y → suc A suc y) A suc y) → (A y → suc A suc y))
22 suceq 4105 . . . . . . . . 9 (A = y → suc A = suc y)
2322a1i 9 . . . . . . . 8 (((A y → suc A suc y) A suc y) → (A = y → suc A = suc y))
2421, 23orim12d 699 . . . . . . 7 (((A y → suc A suc y) A suc y) → ((A y A = y) → (suc A suc y suc A = suc y)))
2520, 24mpd 13 . . . . . 6 (((A y → suc A suc y) A suc y) → (suc A suc y suc A = suc y))
26 vex 2554 . . . . . . . 8 y V
2726sucex 4191 . . . . . . 7 suc y V
2827elsuc2 4110 . . . . . 6 (suc A suc suc y ↔ (suc A suc y suc A = suc y))
2925, 28sylibr 137 . . . . 5 (((A y → suc A suc y) A suc y) → suc A suc suc y)
3029ex 108 . . . 4 ((A y → suc A suc y) → (A suc y → suc A suc suc y))
3130a1i 9 . . 3 (y 𝜔 → ((A y → suc A suc y) → (A suc y → suc A suc suc y)))
324, 8, 12, 16, 18, 31finds 4266 . 2 (B 𝜔 → (A B → suc A suc B))
33 nnon 4275 . . 3 (B 𝜔 → B On)
34 onsucelsucr 4199 . . 3 (B On → (suc A suc BA B))
3533, 34syl 14 . 2 (B 𝜔 → (suc A suc BA B))
3632, 35impbid 120 1 (B 𝜔 → (A B ↔ suc A suc B))
Colors of variables: wff set class
Syntax hints:  wi 4   wa 97  wb 98   wo 628   = wceq 1242   wcel 1390  c0 3218  Oncon0 4066  suc csuc 4068  𝜔com 4256
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 99  ax-ia2 100  ax-ia3 101  ax-in1 544  ax-in2 545  ax-io 629  ax-5 1333  ax-7 1334  ax-gen 1335  ax-ie1 1379  ax-ie2 1380  ax-8 1392  ax-10 1393  ax-11 1394  ax-i12 1395  ax-bnd 1396  ax-4 1397  ax-13 1401  ax-14 1402  ax-17 1416  ax-i9 1420  ax-ial 1424  ax-i5r 1425  ax-ext 2019  ax-sep 3866  ax-nul 3874  ax-pow 3918  ax-pr 3935  ax-un 4136  ax-iinf 4254
This theorem depends on definitions:  df-bi 110  df-3an 886  df-tru 1245  df-nf 1347  df-sb 1643  df-clab 2024  df-cleq 2030  df-clel 2033  df-nfc 2164  df-ral 2305  df-rex 2306  df-v 2553  df-dif 2914  df-un 2916  df-in 2918  df-ss 2925  df-nul 3219  df-pw 3353  df-sn 3373  df-pr 3374  df-uni 3572  df-int 3607  df-tr 3846  df-iord 4069  df-on 4071  df-suc 4074  df-iom 4257
This theorem is referenced by:  nnsucsssuc  6010  nntri3or  6011  nnaordi  6017
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