Intuitionistic Logic Explorer < Previous   Next > Nearby theorems Mirrors  >  Home  >  ILE Home  >  Th. List  >  peano5 GIF version

Theorem peano5 4512
 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. 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 4517. (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 dfom3 4506 . . 3 ω = {𝑦 ∣ (∅ ∈ 𝑦 ∧ ∀𝑥𝑦 suc 𝑥𝑦)}
2 peano1 4508 . . . . . . . 8 ∅ ∈ ω
3 elin 3259 . . . . . . . 8 (∅ ∈ (ω ∩ 𝐴) ↔ (∅ ∈ ω ∧ ∅ ∈ 𝐴))
42, 3mpbiran 924 . . . . . . 7 (∅ ∈ (ω ∩ 𝐴) ↔ ∅ ∈ 𝐴)
54biimpri 132 . . . . . 6 (∅ ∈ 𝐴 → ∅ ∈ (ω ∩ 𝐴))
6 peano2 4509 . . . . . . . . . . . 12 (𝑥 ∈ ω → suc 𝑥 ∈ ω)
76adantr 274 . . . . . . . . . . 11 ((𝑥 ∈ ω ∧ 𝑥𝐴) → suc 𝑥 ∈ ω)
87a1i 9 . . . . . . . . . 10 ((𝑥 ∈ ω → (𝑥𝐴 → suc 𝑥𝐴)) → ((𝑥 ∈ ω ∧ 𝑥𝐴) → suc 𝑥 ∈ ω))
9 pm3.31 260 . . . . . . . . . 10 ((𝑥 ∈ ω → (𝑥𝐴 → suc 𝑥𝐴)) → ((𝑥 ∈ ω ∧ 𝑥𝐴) → suc 𝑥𝐴))
108, 9jcad 305 . . . . . . . . 9 ((𝑥 ∈ ω → (𝑥𝐴 → suc 𝑥𝐴)) → ((𝑥 ∈ ω ∧ 𝑥𝐴) → (suc 𝑥 ∈ ω ∧ suc 𝑥𝐴)))
1110alimi 1431 . . . . . . . 8 (∀𝑥(𝑥 ∈ ω → (𝑥𝐴 → suc 𝑥𝐴)) → ∀𝑥((𝑥 ∈ ω ∧ 𝑥𝐴) → (suc 𝑥 ∈ ω ∧ suc 𝑥𝐴)))
12 df-ral 2421 . . . . . . . 8 (∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴) ↔ ∀𝑥(𝑥 ∈ ω → (𝑥𝐴 → suc 𝑥𝐴)))
13 elin 3259 . . . . . . . . . 10 (𝑥 ∈ (ω ∩ 𝐴) ↔ (𝑥 ∈ ω ∧ 𝑥𝐴))
14 elin 3259 . . . . . . . . . 10 (suc 𝑥 ∈ (ω ∩ 𝐴) ↔ (suc 𝑥 ∈ ω ∧ suc 𝑥𝐴))
1513, 14imbi12i 238 . . . . . . . . 9 ((𝑥 ∈ (ω ∩ 𝐴) → suc 𝑥 ∈ (ω ∩ 𝐴)) ↔ ((𝑥 ∈ ω ∧ 𝑥𝐴) → (suc 𝑥 ∈ ω ∧ suc 𝑥𝐴)))
1615albii 1446 . . . . . . . 8 (∀𝑥(𝑥 ∈ (ω ∩ 𝐴) → suc 𝑥 ∈ (ω ∩ 𝐴)) ↔ ∀𝑥((𝑥 ∈ ω ∧ 𝑥𝐴) → (suc 𝑥 ∈ ω ∧ suc 𝑥𝐴)))
1711, 12, 163imtr4i 200 . . . . . . 7 (∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴) → ∀𝑥(𝑥 ∈ (ω ∩ 𝐴) → suc 𝑥 ∈ (ω ∩ 𝐴)))
18 df-ral 2421 . . . . . . 7 (∀𝑥 ∈ (ω ∩ 𝐴)suc 𝑥 ∈ (ω ∩ 𝐴) ↔ ∀𝑥(𝑥 ∈ (ω ∩ 𝐴) → suc 𝑥 ∈ (ω ∩ 𝐴)))
1917, 18sylibr 133 . . . . . 6 (∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴) → ∀𝑥 ∈ (ω ∩ 𝐴)suc 𝑥 ∈ (ω ∩ 𝐴))
205, 19anim12i 336 . . . . 5 ((∅ ∈ 𝐴 ∧ ∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴)) → (∅ ∈ (ω ∩ 𝐴) ∧ ∀𝑥 ∈ (ω ∩ 𝐴)suc 𝑥 ∈ (ω ∩ 𝐴)))
21 omex 4507 . . . . . . 7 ω ∈ V
2221inex1 4062 . . . . . 6 (ω ∩ 𝐴) ∈ V
23 eleq2 2203 . . . . . . 7 (𝑦 = (ω ∩ 𝐴) → (∅ ∈ 𝑦 ↔ ∅ ∈ (ω ∩ 𝐴)))
24 eleq2 2203 . . . . . . . 8 (𝑦 = (ω ∩ 𝐴) → (suc 𝑥𝑦 ↔ suc 𝑥 ∈ (ω ∩ 𝐴)))
2524raleqbi1dv 2634 . . . . . . 7 (𝑦 = (ω ∩ 𝐴) → (∀𝑥𝑦 suc 𝑥𝑦 ↔ ∀𝑥 ∈ (ω ∩ 𝐴)suc 𝑥 ∈ (ω ∩ 𝐴)))
2623, 25anbi12d 464 . . . . . 6 (𝑦 = (ω ∩ 𝐴) → ((∅ ∈ 𝑦 ∧ ∀𝑥𝑦 suc 𝑥𝑦) ↔ (∅ ∈ (ω ∩ 𝐴) ∧ ∀𝑥 ∈ (ω ∩ 𝐴)suc 𝑥 ∈ (ω ∩ 𝐴))))
2722, 26elab 2828 . . . . 5 ((ω ∩ 𝐴) ∈ {𝑦 ∣ (∅ ∈ 𝑦 ∧ ∀𝑥𝑦 suc 𝑥𝑦)} ↔ (∅ ∈ (ω ∩ 𝐴) ∧ ∀𝑥 ∈ (ω ∩ 𝐴)suc 𝑥 ∈ (ω ∩ 𝐴)))
2820, 27sylibr 133 . . . 4 ((∅ ∈ 𝐴 ∧ ∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴)) → (ω ∩ 𝐴) ∈ {𝑦 ∣ (∅ ∈ 𝑦 ∧ ∀𝑥𝑦 suc 𝑥𝑦)})
29 intss1 3786 . . . 4 ((ω ∩ 𝐴) ∈ {𝑦 ∣ (∅ ∈ 𝑦 ∧ ∀𝑥𝑦 suc 𝑥𝑦)} → {𝑦 ∣ (∅ ∈ 𝑦 ∧ ∀𝑥𝑦 suc 𝑥𝑦)} ⊆ (ω ∩ 𝐴))
3028, 29syl 14 . . 3 ((∅ ∈ 𝐴 ∧ ∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴)) → {𝑦 ∣ (∅ ∈ 𝑦 ∧ ∀𝑥𝑦 suc 𝑥𝑦)} ⊆ (ω ∩ 𝐴))
311, 30eqsstrid 3143 . 2 ((∅ ∈ 𝐴 ∧ ∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴)) → ω ⊆ (ω ∩ 𝐴))
32 ssid 3117 . . . 4 ω ⊆ ω
3332biantrur 301 . . 3 (ω ⊆ 𝐴 ↔ (ω ⊆ ω ∧ ω ⊆ 𝐴))
34 ssin 3298 . . 3 ((ω ⊆ ω ∧ ω ⊆ 𝐴) ↔ ω ⊆ (ω ∩ 𝐴))
3533, 34bitri 183 . 2 (ω ⊆ 𝐴 ↔ ω ⊆ (ω ∩ 𝐴))
3631, 35sylibr 133 1 ((∅ ∈ 𝐴 ∧ ∀𝑥 ∈ ω (𝑥𝐴 → suc 𝑥𝐴)) → ω ⊆ 𝐴)
 Colors of variables: wff set class Syntax hints:   → wi 4   ∧ wa 103  ∀wal 1329   = wceq 1331   ∈ wcel 1480  {cab 2125  ∀wral 2416   ∩ cin 3070   ⊆ wss 3071  ∅c0 3363  ∩ cint 3771  suc csuc 4287  ωcom 4504 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 105  ax-ia2 106  ax-ia3 107  ax-in1 603  ax-in2 604  ax-io 698  ax-5 1423  ax-7 1424  ax-gen 1425  ax-ie1 1469  ax-ie2 1470  ax-8 1482  ax-10 1483  ax-11 1484  ax-i12 1485  ax-bndl 1486  ax-4 1487  ax-13 1491  ax-14 1492  ax-17 1506  ax-i9 1510  ax-ial 1514  ax-i5r 1515  ax-ext 2121  ax-sep 4046  ax-nul 4054  ax-pow 4098  ax-pr 4131  ax-un 4355  ax-iinf 4502 This theorem depends on definitions:  df-bi 116  df-3an 964  df-tru 1334  df-nf 1437  df-sb 1736  df-clab 2126  df-cleq 2132  df-clel 2135  df-nfc 2270  df-ral 2421  df-rex 2422  df-v 2688  df-dif 3073  df-un 3075  df-in 3077  df-ss 3084  df-nul 3364  df-pw 3512  df-sn 3533  df-pr 3534  df-uni 3737  df-int 3772  df-suc 4293  df-iom 4505 This theorem is referenced by:  find  4513  finds  4514  finds2  4515  indpi  7157
 Copyright terms: Public domain W3C validator