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Theorem peano5 7367
Description: The induction postulate: any class containing zero and closed under the successor operation contains all natural numbers. One of Peano's five postulates for arithmetic. Proposition 7.30(5) of [TakeutiZaring] p. 43, except our proof does not require the Axiom of Infinity. The more traditional statement of mathematical induction as a theorem schema, with a basis and an induction step, is derived from this theorem as theorem findes 7374. (Contributed by NM, 18-Feb-2004.)
Assertion
Ref Expression
peano5 ((∅ ∈ 𝐴 ∧ ∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴)) → ω ⊆ 𝐴)
Distinct variable group:   𝑥,𝐴

Proof of Theorem peano5
Dummy variable 𝑦 is distinct from all other variables.
StepHypRef Expression
1 eldifn 3956 . . . . . 6 (𝑦 ∈ (ω ∖ 𝐴) → ¬ 𝑦𝐴)
21adantl 475 . . . . 5 (((∅ ∈ 𝐴 ∧ ∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴)) ∧ 𝑦 ∈ (ω ∖ 𝐴)) → ¬ 𝑦𝐴)
3 eldifi 3955 . . . . . . . 8 (𝑦 ∈ (ω ∖ 𝐴) → 𝑦 ∈ ω)
4 elndif 3957 . . . . . . . . 9 (∅ ∈ 𝐴 → ¬ ∅ ∈ (ω ∖ 𝐴))
5 eleq1 2847 . . . . . . . . . . 11 (𝑦 = ∅ → (𝑦 ∈ (ω ∖ 𝐴) ↔ ∅ ∈ (ω ∖ 𝐴)))
65biimpcd 241 . . . . . . . . . 10 (𝑦 ∈ (ω ∖ 𝐴) → (𝑦 = ∅ → ∅ ∈ (ω ∖ 𝐴)))
76necon3bd 2983 . . . . . . . . 9 (𝑦 ∈ (ω ∖ 𝐴) → (¬ ∅ ∈ (ω ∖ 𝐴) → 𝑦 ≠ ∅))
84, 7mpan9 502 . . . . . . . 8 ((∅ ∈ 𝐴𝑦 ∈ (ω ∖ 𝐴)) → 𝑦 ≠ ∅)
9 nnsuc 7360 . . . . . . . 8 ((𝑦 ∈ ω ∧ 𝑦 ≠ ∅) → ∃𝑥 ∈ ω 𝑦 = suc 𝑥)
103, 8, 9syl2an2 676 . . . . . . 7 ((∅ ∈ 𝐴𝑦 ∈ (ω ∖ 𝐴)) → ∃𝑥 ∈ ω 𝑦 = suc 𝑥)
1110ad4ant13 741 . . . . . 6 ((((∅ ∈ 𝐴 ∧ ∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴)) ∧ 𝑦 ∈ (ω ∖ 𝐴)) ∧ ((ω ∖ 𝐴) ∩ 𝑦) = ∅) → ∃𝑥 ∈ ω 𝑦 = suc 𝑥)
12 nfra1 3123 . . . . . . . . . . 11 𝑥𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴)
13 nfv 1957 . . . . . . . . . . 11 𝑥(𝑦 ∈ (ω ∖ 𝐴) ∧ ((ω ∖ 𝐴) ∩ 𝑦) = ∅)
1412, 13nfan 1946 . . . . . . . . . 10 𝑥(∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴) ∧ (𝑦 ∈ (ω ∖ 𝐴) ∧ ((ω ∖ 𝐴) ∩ 𝑦) = ∅))
15 nfv 1957 . . . . . . . . . 10 𝑥 𝑦𝐴
16 rsp 3111 . . . . . . . . . . 11 (∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴) → (𝑥 ∈ ω → (𝑥𝐴 → suc 𝑥𝐴)))
17 vex 3401 . . . . . . . . . . . . . . . . . 18 𝑥 ∈ V
1817sucid 6055 . . . . . . . . . . . . . . . . 17 𝑥 ∈ suc 𝑥
19 eleq2 2848 . . . . . . . . . . . . . . . . 17 (𝑦 = suc 𝑥 → (𝑥𝑦𝑥 ∈ suc 𝑥))
2018, 19mpbiri 250 . . . . . . . . . . . . . . . 16 (𝑦 = suc 𝑥𝑥𝑦)
21 eleq1 2847 . . . . . . . . . . . . . . . . . 18 (𝑦 = suc 𝑥 → (𝑦 ∈ ω ↔ suc 𝑥 ∈ ω))
22 peano2b 7359 . . . . . . . . . . . . . . . . . 18 (𝑥 ∈ ω ↔ suc 𝑥 ∈ ω)
2321, 22syl6bbr 281 . . . . . . . . . . . . . . . . 17 (𝑦 = suc 𝑥 → (𝑦 ∈ ω ↔ 𝑥 ∈ ω))
24 minel 4258 . . . . . . . . . . . . . . . . . . 19 ((𝑥𝑦 ∧ ((ω ∖ 𝐴) ∩ 𝑦) = ∅) → ¬ 𝑥 ∈ (ω ∖ 𝐴))
25 neldif 3958 . . . . . . . . . . . . . . . . . . 19 ((𝑥 ∈ ω ∧ ¬ 𝑥 ∈ (ω ∖ 𝐴)) → 𝑥𝐴)
2624, 25sylan2 586 . . . . . . . . . . . . . . . . . 18 ((𝑥 ∈ ω ∧ (𝑥𝑦 ∧ ((ω ∖ 𝐴) ∩ 𝑦) = ∅)) → 𝑥𝐴)
2726exp32 413 . . . . . . . . . . . . . . . . 17 (𝑥 ∈ ω → (𝑥𝑦 → (((ω ∖ 𝐴) ∩ 𝑦) = ∅ → 𝑥𝐴)))
2823, 27syl6bi 245 . . . . . . . . . . . . . . . 16 (𝑦 = suc 𝑥 → (𝑦 ∈ ω → (𝑥𝑦 → (((ω ∖ 𝐴) ∩ 𝑦) = ∅ → 𝑥𝐴))))
2920, 28mpid 44 . . . . . . . . . . . . . . 15 (𝑦 = suc 𝑥 → (𝑦 ∈ ω → (((ω ∖ 𝐴) ∩ 𝑦) = ∅ → 𝑥𝐴)))
303, 29syl5 34 . . . . . . . . . . . . . 14 (𝑦 = suc 𝑥 → (𝑦 ∈ (ω ∖ 𝐴) → (((ω ∖ 𝐴) ∩ 𝑦) = ∅ → 𝑥𝐴)))
3130impd 400 . . . . . . . . . . . . 13 (𝑦 = suc 𝑥 → ((𝑦 ∈ (ω ∖ 𝐴) ∧ ((ω ∖ 𝐴) ∩ 𝑦) = ∅) → 𝑥𝐴))
32 eleq1a 2854 . . . . . . . . . . . . . 14 (suc 𝑥𝐴 → (𝑦 = suc 𝑥𝑦𝐴))
3332com12 32 . . . . . . . . . . . . 13 (𝑦 = suc 𝑥 → (suc 𝑥𝐴𝑦𝐴))
3431, 33imim12d 81 . . . . . . . . . . . 12 (𝑦 = suc 𝑥 → ((𝑥𝐴 → suc 𝑥𝐴) → ((𝑦 ∈ (ω ∖ 𝐴) ∧ ((ω ∖ 𝐴) ∩ 𝑦) = ∅) → 𝑦𝐴)))
3534com13 88 . . . . . . . . . . 11 ((𝑦 ∈ (ω ∖ 𝐴) ∧ ((ω ∖ 𝐴) ∩ 𝑦) = ∅) → ((𝑥𝐴 → suc 𝑥𝐴) → (𝑦 = suc 𝑥𝑦𝐴)))
3616, 35sylan9 503 . . . . . . . . . 10 ((∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴) ∧ (𝑦 ∈ (ω ∖ 𝐴) ∧ ((ω ∖ 𝐴) ∩ 𝑦) = ∅)) → (𝑥 ∈ ω → (𝑦 = suc 𝑥𝑦𝐴)))
3714, 15, 36rexlimd 3208 . . . . . . . . 9 ((∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴) ∧ (𝑦 ∈ (ω ∖ 𝐴) ∧ ((ω ∖ 𝐴) ∩ 𝑦) = ∅)) → (∃𝑥 ∈ ω 𝑦 = suc 𝑥𝑦𝐴))
3837exp32 413 . . . . . . . 8 (∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴) → (𝑦 ∈ (ω ∖ 𝐴) → (((ω ∖ 𝐴) ∩ 𝑦) = ∅ → (∃𝑥 ∈ ω 𝑦 = suc 𝑥𝑦𝐴))))
3938a1i 11 . . . . . . 7 (∅ ∈ 𝐴 → (∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴) → (𝑦 ∈ (ω ∖ 𝐴) → (((ω ∖ 𝐴) ∩ 𝑦) = ∅ → (∃𝑥 ∈ ω 𝑦 = suc 𝑥𝑦𝐴)))))
4039imp41 418 . . . . . 6 ((((∅ ∈ 𝐴 ∧ ∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴)) ∧ 𝑦 ∈ (ω ∖ 𝐴)) ∧ ((ω ∖ 𝐴) ∩ 𝑦) = ∅) → (∃𝑥 ∈ ω 𝑦 = suc 𝑥𝑦𝐴))
4111, 40mpd 15 . . . . 5 ((((∅ ∈ 𝐴 ∧ ∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴)) ∧ 𝑦 ∈ (ω ∖ 𝐴)) ∧ ((ω ∖ 𝐴) ∩ 𝑦) = ∅) → 𝑦𝐴)
422, 41mtand 806 . . . 4 (((∅ ∈ 𝐴 ∧ ∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴)) ∧ 𝑦 ∈ (ω ∖ 𝐴)) → ¬ ((ω ∖ 𝐴) ∩ 𝑦) = ∅)
4342nrexdv 3182 . . 3 ((∅ ∈ 𝐴 ∧ ∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴)) → ¬ ∃𝑦 ∈ (ω ∖ 𝐴)((ω ∖ 𝐴) ∩ 𝑦) = ∅)
44 ordom 7352 . . . . 5 Ord ω
45 difss 3960 . . . . 5 (ω ∖ 𝐴) ⊆ ω
46 tz7.5 5997 . . . . 5 ((Ord ω ∧ (ω ∖ 𝐴) ⊆ ω ∧ (ω ∖ 𝐴) ≠ ∅) → ∃𝑦 ∈ (ω ∖ 𝐴)((ω ∖ 𝐴) ∩ 𝑦) = ∅)
4744, 45, 46mp3an12 1524 . . . 4 ((ω ∖ 𝐴) ≠ ∅ → ∃𝑦 ∈ (ω ∖ 𝐴)((ω ∖ 𝐴) ∩ 𝑦) = ∅)
4847necon1bi 2997 . . 3 (¬ ∃𝑦 ∈ (ω ∖ 𝐴)((ω ∖ 𝐴) ∩ 𝑦) = ∅ → (ω ∖ 𝐴) = ∅)
4943, 48syl 17 . 2 ((∅ ∈ 𝐴 ∧ ∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴)) → (ω ∖ 𝐴) = ∅)
50 ssdif0 4172 . 2 (ω ⊆ 𝐴 ↔ (ω ∖ 𝐴) = ∅)
5149, 50sylibr 226 1 ((∅ ∈ 𝐴 ∧ ∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴)) → ω ⊆ 𝐴)
Colors of variables: wff setvar class
Syntax hints:  ¬ wn 3  wi 4  wa 386   = wceq 1601  wcel 2107  wne 2969  wral 3090  wrex 3091  cdif 3789  cin 3791  wss 3792  c0 4141  Ord word 5975  suc csuc 5978  ωcom 7343
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1839  ax-4 1853  ax-5 1953  ax-6 2021  ax-7 2055  ax-8 2109  ax-9 2116  ax-10 2135  ax-11 2150  ax-12 2163  ax-13 2334  ax-ext 2754  ax-sep 5017  ax-nul 5025  ax-pr 5138  ax-un 7226
This theorem depends on definitions:  df-bi 199  df-an 387  df-or 837  df-3or 1072  df-3an 1073  df-tru 1605  df-ex 1824  df-nf 1828  df-sb 2012  df-mo 2551  df-eu 2587  df-clab 2764  df-cleq 2770  df-clel 2774  df-nfc 2921  df-ne 2970  df-ral 3095  df-rex 3096  df-rab 3099  df-v 3400  df-sbc 3653  df-dif 3795  df-un 3797  df-in 3799  df-ss 3806  df-pss 3808  df-nul 4142  df-if 4308  df-pw 4381  df-sn 4399  df-pr 4401  df-tp 4403  df-op 4405  df-uni 4672  df-br 4887  df-opab 4949  df-tr 4988  df-eprel 5266  df-po 5274  df-so 5275  df-fr 5314  df-we 5316  df-ord 5979  df-on 5980  df-lim 5981  df-suc 5982  df-om 7344
This theorem is referenced by:  find  7369  finds  7370  finds2  7372  omex  8837  dfom3  8841
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