MPE Home Metamath Proof Explorer < Previous   Next >
Nearby theorems
Mirrors  >  Home  >  MPE Home  >  Th. List  >  peano5 Structured version   Visualization version   GIF version

Theorem peano5 7604
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 7611. (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 4103 . . . . . 6 (𝑦 ∈ (ω ∖ 𝐴) → ¬ 𝑦𝐴)
21adantl 484 . . . . 5 (((∅ ∈ 𝐴 ∧ ∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴)) ∧ 𝑦 ∈ (ω ∖ 𝐴)) → ¬ 𝑦𝐴)
3 eldifi 4102 . . . . . . . 8 (𝑦 ∈ (ω ∖ 𝐴) → 𝑦 ∈ ω)
4 elndif 4104 . . . . . . . . 9 (∅ ∈ 𝐴 → ¬ ∅ ∈ (ω ∖ 𝐴))
5 eleq1 2900 . . . . . . . . . . 11 (𝑦 = ∅ → (𝑦 ∈ (ω ∖ 𝐴) ↔ ∅ ∈ (ω ∖ 𝐴)))
65biimpcd 251 . . . . . . . . . 10 (𝑦 ∈ (ω ∖ 𝐴) → (𝑦 = ∅ → ∅ ∈ (ω ∖ 𝐴)))
76necon3bd 3030 . . . . . . . . 9 (𝑦 ∈ (ω ∖ 𝐴) → (¬ ∅ ∈ (ω ∖ 𝐴) → 𝑦 ≠ ∅))
84, 7mpan9 509 . . . . . . . 8 ((∅ ∈ 𝐴𝑦 ∈ (ω ∖ 𝐴)) → 𝑦 ≠ ∅)
9 nnsuc 7596 . . . . . . . 8 ((𝑦 ∈ ω ∧ 𝑦 ≠ ∅) → ∃𝑥 ∈ ω 𝑦 = suc 𝑥)
103, 8, 9syl2an2 684 . . . . . . 7 ((∅ ∈ 𝐴𝑦 ∈ (ω ∖ 𝐴)) → ∃𝑥 ∈ ω 𝑦 = suc 𝑥)
1110ad4ant13 749 . . . . . 6 ((((∅ ∈ 𝐴 ∧ ∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴)) ∧ 𝑦 ∈ (ω ∖ 𝐴)) ∧ ((ω ∖ 𝐴) ∩ 𝑦) = ∅) → ∃𝑥 ∈ ω 𝑦 = suc 𝑥)
12 nfra1 3219 . . . . . . . . . . 11 𝑥𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴)
13 nfv 1911 . . . . . . . . . . 11 𝑥(𝑦 ∈ (ω ∖ 𝐴) ∧ ((ω ∖ 𝐴) ∩ 𝑦) = ∅)
1412, 13nfan 1896 . . . . . . . . . 10 𝑥(∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴) ∧ (𝑦 ∈ (ω ∖ 𝐴) ∧ ((ω ∖ 𝐴) ∩ 𝑦) = ∅))
15 nfv 1911 . . . . . . . . . 10 𝑥 𝑦𝐴
16 rsp 3205 . . . . . . . . . . 11 (∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴) → (𝑥 ∈ ω → (𝑥𝐴 → suc 𝑥𝐴)))
17 vex 3497 . . . . . . . . . . . . . . . . . 18 𝑥 ∈ V
1817sucid 6269 . . . . . . . . . . . . . . . . 17 𝑥 ∈ suc 𝑥
19 eleq2 2901 . . . . . . . . . . . . . . . . 17 (𝑦 = suc 𝑥 → (𝑥𝑦𝑥 ∈ suc 𝑥))
2018, 19mpbiri 260 . . . . . . . . . . . . . . . 16 (𝑦 = suc 𝑥𝑥𝑦)
21 eleq1 2900 . . . . . . . . . . . . . . . . . 18 (𝑦 = suc 𝑥 → (𝑦 ∈ ω ↔ suc 𝑥 ∈ ω))
22 peano2b 7595 . . . . . . . . . . . . . . . . . 18 (𝑥 ∈ ω ↔ suc 𝑥 ∈ ω)
2321, 22syl6bbr 291 . . . . . . . . . . . . . . . . 17 (𝑦 = suc 𝑥 → (𝑦 ∈ ω ↔ 𝑥 ∈ ω))
24 minel 4414 . . . . . . . . . . . . . . . . . . 19 ((𝑥𝑦 ∧ ((ω ∖ 𝐴) ∩ 𝑦) = ∅) → ¬ 𝑥 ∈ (ω ∖ 𝐴))
25 neldif 4105 . . . . . . . . . . . . . . . . . . 19 ((𝑥 ∈ ω ∧ ¬ 𝑥 ∈ (ω ∖ 𝐴)) → 𝑥𝐴)
2624, 25sylan2 594 . . . . . . . . . . . . . . . . . 18 ((𝑥 ∈ ω ∧ (𝑥𝑦 ∧ ((ω ∖ 𝐴) ∩ 𝑦) = ∅)) → 𝑥𝐴)
2726exp32 423 . . . . . . . . . . . . . . . . 17 (𝑥 ∈ ω → (𝑥𝑦 → (((ω ∖ 𝐴) ∩ 𝑦) = ∅ → 𝑥𝐴)))
2823, 27syl6bi 255 . . . . . . . . . . . . . . . 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 413 . . . . . . . . . . . . 13 (𝑦 = suc 𝑥 → ((𝑦 ∈ (ω ∖ 𝐴) ∧ ((ω ∖ 𝐴) ∩ 𝑦) = ∅) → 𝑥𝐴))
32 eleq1a 2908 . . . . . . . . . . . . . 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 510 . . . . . . . . . 10 ((∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴) ∧ (𝑦 ∈ (ω ∖ 𝐴) ∧ ((ω ∖ 𝐴) ∩ 𝑦) = ∅)) → (𝑥 ∈ ω → (𝑦 = suc 𝑥𝑦𝐴)))
3714, 15, 36rexlimd 3317 . . . . . . . . 9 ((∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴) ∧ (𝑦 ∈ (ω ∖ 𝐴) ∧ ((ω ∖ 𝐴) ∩ 𝑦) = ∅)) → (∃𝑥 ∈ ω 𝑦 = suc 𝑥𝑦𝐴))
3837exp32 423 . . . . . . . 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 428 . . . . . 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 814 . . . 4 (((∅ ∈ 𝐴 ∧ ∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴)) ∧ 𝑦 ∈ (ω ∖ 𝐴)) → ¬ ((ω ∖ 𝐴) ∩ 𝑦) = ∅)
4342nrexdv 3270 . . 3 ((∅ ∈ 𝐴 ∧ ∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴)) → ¬ ∃𝑦 ∈ (ω ∖ 𝐴)((ω ∖ 𝐴) ∩ 𝑦) = ∅)
44 ordom 7588 . . . . 5 Ord ω
45 difss 4107 . . . . 5 (ω ∖ 𝐴) ⊆ ω
46 tz7.5 6211 . . . . 5 ((Ord ω ∧ (ω ∖ 𝐴) ⊆ ω ∧ (ω ∖ 𝐴) ≠ ∅) → ∃𝑦 ∈ (ω ∖ 𝐴)((ω ∖ 𝐴) ∩ 𝑦) = ∅)
4744, 45, 46mp3an12 1447 . . . 4 ((ω ∖ 𝐴) ≠ ∅ → ∃𝑦 ∈ (ω ∖ 𝐴)((ω ∖ 𝐴) ∩ 𝑦) = ∅)
4847necon1bi 3044 . . 3 (¬ ∃𝑦 ∈ (ω ∖ 𝐴)((ω ∖ 𝐴) ∩ 𝑦) = ∅ → (ω ∖ 𝐴) = ∅)
4943, 48syl 17 . 2 ((∅ ∈ 𝐴 ∧ ∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴)) → (ω ∖ 𝐴) = ∅)
50 ssdif0 4322 . 2 (ω ⊆ 𝐴 ↔ (ω ∖ 𝐴) = ∅)
5149, 50sylibr 236 1 ((∅ ∈ 𝐴 ∧ ∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴)) → ω ⊆ 𝐴)
Colors of variables: wff setvar class
Syntax hints:  ¬ wn 3  wi 4  wa 398   = wceq 1533  wcel 2110  wne 3016  wral 3138  wrex 3139  cdif 3932  cin 3934  wss 3935  c0 4290  Ord word 6189  suc csuc 6192  ωcom 7579
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1792  ax-4 1806  ax-5 1907  ax-6 1966  ax-7 2011  ax-8 2112  ax-9 2120  ax-10 2141  ax-11 2157  ax-12 2173  ax-ext 2793  ax-sep 5202  ax-nul 5209  ax-pr 5329  ax-un 7460
This theorem depends on definitions:  df-bi 209  df-an 399  df-or 844  df-3or 1084  df-3an 1085  df-tru 1536  df-ex 1777  df-nf 1781  df-sb 2066  df-mo 2618  df-eu 2650  df-clab 2800  df-cleq 2814  df-clel 2893  df-nfc 2963  df-ne 3017  df-ral 3143  df-rex 3144  df-rab 3147  df-v 3496  df-sbc 3772  df-dif 3938  df-un 3940  df-in 3942  df-ss 3951  df-pss 3953  df-nul 4291  df-if 4467  df-pw 4540  df-sn 4567  df-pr 4569  df-tp 4571  df-op 4573  df-uni 4838  df-br 5066  df-opab 5128  df-tr 5172  df-eprel 5464  df-po 5473  df-so 5474  df-fr 5513  df-we 5515  df-ord 6193  df-on 6194  df-lim 6195  df-suc 6196  df-om 7580
This theorem is referenced by:  find  7606  finds  7607  finds2  7609  omex  9105  dfom3  9109
  Copyright terms: Public domain W3C validator