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Theorem peano5 7237
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 7244. (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 3885 . . . . . 6 (𝑦 ∈ (ω ∖ 𝐴) → ¬ 𝑦𝐴)
21adantl 467 . . . . 5 (((∅ ∈ 𝐴 ∧ ∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴)) ∧ 𝑦 ∈ (ω ∖ 𝐴)) → ¬ 𝑦𝐴)
3 eldifi 3884 . . . . . . . . . 10 (𝑦 ∈ (ω ∖ 𝐴) → 𝑦 ∈ ω)
43adantl 467 . . . . . . . . 9 ((∅ ∈ 𝐴𝑦 ∈ (ω ∖ 𝐴)) → 𝑦 ∈ ω)
5 elndif 3886 . . . . . . . . . 10 (∅ ∈ 𝐴 → ¬ ∅ ∈ (ω ∖ 𝐴))
6 eleq1 2838 . . . . . . . . . . . 12 (𝑦 = ∅ → (𝑦 ∈ (ω ∖ 𝐴) ↔ ∅ ∈ (ω ∖ 𝐴)))
76biimpcd 239 . . . . . . . . . . 11 (𝑦 ∈ (ω ∖ 𝐴) → (𝑦 = ∅ → ∅ ∈ (ω ∖ 𝐴)))
87necon3bd 2957 . . . . . . . . . 10 (𝑦 ∈ (ω ∖ 𝐴) → (¬ ∅ ∈ (ω ∖ 𝐴) → 𝑦 ≠ ∅))
95, 8mpan9 492 . . . . . . . . 9 ((∅ ∈ 𝐴𝑦 ∈ (ω ∖ 𝐴)) → 𝑦 ≠ ∅)
10 nnsuc 7230 . . . . . . . . 9 ((𝑦 ∈ ω ∧ 𝑦 ≠ ∅) → ∃𝑥 ∈ ω 𝑦 = suc 𝑥)
114, 9, 10syl2anc 567 . . . . . . . 8 ((∅ ∈ 𝐴𝑦 ∈ (ω ∖ 𝐴)) → ∃𝑥 ∈ ω 𝑦 = suc 𝑥)
1211adantlr 688 . . . . . . 7 (((∅ ∈ 𝐴 ∧ ∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴)) ∧ 𝑦 ∈ (ω ∖ 𝐴)) → ∃𝑥 ∈ ω 𝑦 = suc 𝑥)
1312adantr 466 . . . . . 6 ((((∅ ∈ 𝐴 ∧ ∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴)) ∧ 𝑦 ∈ (ω ∖ 𝐴)) ∧ ((ω ∖ 𝐴) ∩ 𝑦) = ∅) → ∃𝑥 ∈ ω 𝑦 = suc 𝑥)
14 nfra1 3090 . . . . . . . . . . 11 𝑥𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴)
15 nfv 1995 . . . . . . . . . . 11 𝑥(𝑦 ∈ (ω ∖ 𝐴) ∧ ((ω ∖ 𝐴) ∩ 𝑦) = ∅)
1614, 15nfan 1980 . . . . . . . . . 10 𝑥(∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴) ∧ (𝑦 ∈ (ω ∖ 𝐴) ∧ ((ω ∖ 𝐴) ∩ 𝑦) = ∅))
17 nfv 1995 . . . . . . . . . 10 𝑥 𝑦𝐴
18 rsp 3078 . . . . . . . . . . 11 (∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴) → (𝑥 ∈ ω → (𝑥𝐴 → suc 𝑥𝐴)))
19 vex 3354 . . . . . . . . . . . . . . . . . 18 𝑥 ∈ V
2019sucid 5948 . . . . . . . . . . . . . . . . 17 𝑥 ∈ suc 𝑥
21 eleq2 2839 . . . . . . . . . . . . . . . . 17 (𝑦 = suc 𝑥 → (𝑥𝑦𝑥 ∈ suc 𝑥))
2220, 21mpbiri 248 . . . . . . . . . . . . . . . 16 (𝑦 = suc 𝑥𝑥𝑦)
23 eleq1 2838 . . . . . . . . . . . . . . . . . 18 (𝑦 = suc 𝑥 → (𝑦 ∈ ω ↔ suc 𝑥 ∈ ω))
24 peano2b 7229 . . . . . . . . . . . . . . . . . 18 (𝑥 ∈ ω ↔ suc 𝑥 ∈ ω)
2523, 24syl6bbr 278 . . . . . . . . . . . . . . . . 17 (𝑦 = suc 𝑥 → (𝑦 ∈ ω ↔ 𝑥 ∈ ω))
26 minel 4177 . . . . . . . . . . . . . . . . . . 19 ((𝑥𝑦 ∧ ((ω ∖ 𝐴) ∩ 𝑦) = ∅) → ¬ 𝑥 ∈ (ω ∖ 𝐴))
27 neldif 3887 . . . . . . . . . . . . . . . . . . 19 ((𝑥 ∈ ω ∧ ¬ 𝑥 ∈ (ω ∖ 𝐴)) → 𝑥𝐴)
2826, 27sylan2 574 . . . . . . . . . . . . . . . . . 18 ((𝑥 ∈ ω ∧ (𝑥𝑦 ∧ ((ω ∖ 𝐴) ∩ 𝑦) = ∅)) → 𝑥𝐴)
2928exp32 407 . . . . . . . . . . . . . . . . 17 (𝑥 ∈ ω → (𝑥𝑦 → (((ω ∖ 𝐴) ∩ 𝑦) = ∅ → 𝑥𝐴)))
3025, 29syl6bi 243 . . . . . . . . . . . . . . . 16 (𝑦 = suc 𝑥 → (𝑦 ∈ ω → (𝑥𝑦 → (((ω ∖ 𝐴) ∩ 𝑦) = ∅ → 𝑥𝐴))))
3122, 30mpid 44 . . . . . . . . . . . . . . 15 (𝑦 = suc 𝑥 → (𝑦 ∈ ω → (((ω ∖ 𝐴) ∩ 𝑦) = ∅ → 𝑥𝐴)))
323, 31syl5 34 . . . . . . . . . . . . . 14 (𝑦 = suc 𝑥 → (𝑦 ∈ (ω ∖ 𝐴) → (((ω ∖ 𝐴) ∩ 𝑦) = ∅ → 𝑥𝐴)))
3332impd 396 . . . . . . . . . . . . 13 (𝑦 = suc 𝑥 → ((𝑦 ∈ (ω ∖ 𝐴) ∧ ((ω ∖ 𝐴) ∩ 𝑦) = ∅) → 𝑥𝐴))
34 eleq1a 2845 . . . . . . . . . . . . . 14 (suc 𝑥𝐴 → (𝑦 = suc 𝑥𝑦𝐴))
3534com12 32 . . . . . . . . . . . . 13 (𝑦 = suc 𝑥 → (suc 𝑥𝐴𝑦𝐴))
3633, 35imim12d 81 . . . . . . . . . . . 12 (𝑦 = suc 𝑥 → ((𝑥𝐴 → suc 𝑥𝐴) → ((𝑦 ∈ (ω ∖ 𝐴) ∧ ((ω ∖ 𝐴) ∩ 𝑦) = ∅) → 𝑦𝐴)))
3736com13 88 . . . . . . . . . . 11 ((𝑦 ∈ (ω ∖ 𝐴) ∧ ((ω ∖ 𝐴) ∩ 𝑦) = ∅) → ((𝑥𝐴 → suc 𝑥𝐴) → (𝑦 = suc 𝑥𝑦𝐴)))
3818, 37sylan9 493 . . . . . . . . . 10 ((∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴) ∧ (𝑦 ∈ (ω ∖ 𝐴) ∧ ((ω ∖ 𝐴) ∩ 𝑦) = ∅)) → (𝑥 ∈ ω → (𝑦 = suc 𝑥𝑦𝐴)))
3916, 17, 38rexlimd 3174 . . . . . . . . 9 ((∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴) ∧ (𝑦 ∈ (ω ∖ 𝐴) ∧ ((ω ∖ 𝐴) ∩ 𝑦) = ∅)) → (∃𝑥 ∈ ω 𝑦 = suc 𝑥𝑦𝐴))
4039exp32 407 . . . . . . . 8 (∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴) → (𝑦 ∈ (ω ∖ 𝐴) → (((ω ∖ 𝐴) ∩ 𝑦) = ∅ → (∃𝑥 ∈ ω 𝑦 = suc 𝑥𝑦𝐴))))
4140a1i 11 . . . . . . 7 (∅ ∈ 𝐴 → (∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴) → (𝑦 ∈ (ω ∖ 𝐴) → (((ω ∖ 𝐴) ∩ 𝑦) = ∅ → (∃𝑥 ∈ ω 𝑦 = suc 𝑥𝑦𝐴)))))
4241imp41 412 . . . . . 6 ((((∅ ∈ 𝐴 ∧ ∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴)) ∧ 𝑦 ∈ (ω ∖ 𝐴)) ∧ ((ω ∖ 𝐴) ∩ 𝑦) = ∅) → (∃𝑥 ∈ ω 𝑦 = suc 𝑥𝑦𝐴))
4313, 42mpd 15 . . . . 5 ((((∅ ∈ 𝐴 ∧ ∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴)) ∧ 𝑦 ∈ (ω ∖ 𝐴)) ∧ ((ω ∖ 𝐴) ∩ 𝑦) = ∅) → 𝑦𝐴)
442, 43mtand 810 . . . 4 (((∅ ∈ 𝐴 ∧ ∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴)) ∧ 𝑦 ∈ (ω ∖ 𝐴)) → ¬ ((ω ∖ 𝐴) ∩ 𝑦) = ∅)
4544nrexdv 3149 . . 3 ((∅ ∈ 𝐴 ∧ ∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴)) → ¬ ∃𝑦 ∈ (ω ∖ 𝐴)((ω ∖ 𝐴) ∩ 𝑦) = ∅)
46 ordom 7222 . . . . 5 Ord ω
47 difss 3889 . . . . 5 (ω ∖ 𝐴) ⊆ ω
48 tz7.5 5888 . . . . 5 ((Ord ω ∧ (ω ∖ 𝐴) ⊆ ω ∧ (ω ∖ 𝐴) ≠ ∅) → ∃𝑦 ∈ (ω ∖ 𝐴)((ω ∖ 𝐴) ∩ 𝑦) = ∅)
4946, 47, 48mp3an12 1562 . . . 4 ((ω ∖ 𝐴) ≠ ∅ → ∃𝑦 ∈ (ω ∖ 𝐴)((ω ∖ 𝐴) ∩ 𝑦) = ∅)
5049necon1bi 2971 . . 3 (¬ ∃𝑦 ∈ (ω ∖ 𝐴)((ω ∖ 𝐴) ∩ 𝑦) = ∅ → (ω ∖ 𝐴) = ∅)
5145, 50syl 17 . 2 ((∅ ∈ 𝐴 ∧ ∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴)) → (ω ∖ 𝐴) = ∅)
52 ssdif0 4090 . 2 (ω ⊆ 𝐴 ↔ (ω ∖ 𝐴) = ∅)
5351, 52sylibr 224 1 ((∅ ∈ 𝐴 ∧ ∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴)) → ω ⊆ 𝐴)
Colors of variables: wff setvar class
Syntax hints:  ¬ wn 3  wi 4  wa 382   = wceq 1631  wcel 2145  wne 2943  wral 3061  wrex 3062  cdif 3721  cin 3723  wss 3724  c0 4064  Ord word 5866  suc csuc 5869  ωcom 7213
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1870  ax-4 1885  ax-5 1991  ax-6 2057  ax-7 2093  ax-8 2147  ax-9 2154  ax-10 2174  ax-11 2190  ax-12 2203  ax-13 2408  ax-ext 2751  ax-sep 4916  ax-nul 4924  ax-pr 5035  ax-un 7097
This theorem depends on definitions:  df-bi 197  df-an 383  df-or 829  df-3or 1072  df-3an 1073  df-tru 1634  df-ex 1853  df-nf 1858  df-sb 2050  df-eu 2622  df-mo 2623  df-clab 2758  df-cleq 2764  df-clel 2767  df-nfc 2902  df-ne 2944  df-ral 3066  df-rex 3067  df-rab 3070  df-v 3353  df-sbc 3589  df-dif 3727  df-un 3729  df-in 3731  df-ss 3738  df-pss 3740  df-nul 4065  df-if 4227  df-pw 4300  df-sn 4318  df-pr 4320  df-tp 4322  df-op 4324  df-uni 4576  df-br 4788  df-opab 4848  df-tr 4888  df-eprel 5163  df-po 5171  df-so 5172  df-fr 5209  df-we 5211  df-ord 5870  df-on 5871  df-lim 5872  df-suc 5873  df-om 7214
This theorem is referenced by:  find  7239  finds  7240  finds2  7242  omex  8705  dfom3  8709
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