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Mirrors > Home > MPE Home > Th. List > peano1 | Structured version Visualization version GIF version |
Description: Zero is a natural number. One of Peano's five postulates for arithmetic. Proposition 7.30(1) of [TakeutiZaring] p. 42. Note: Unlike most textbooks, our proofs of peano1 7881 through peano5 7886 do not use the Axiom of Infinity. Unlike Takeuti and Zaring, they also do not use the Axiom of Regularity. (Contributed by NM, 15-May-1994.) Avoid ax-un 7727. (Revised by BTernaryTau, 29-Nov-2024.) |
Ref | Expression |
---|---|
peano1 | ⊢ ∅ ∈ ω |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | 0elon 6418 | . 2 ⊢ ∅ ∈ On | |
2 | 0ellim 6427 | . . 3 ⊢ (Lim 𝑥 → ∅ ∈ 𝑥) | |
3 | 2 | ax-gen 1797 | . 2 ⊢ ∀𝑥(Lim 𝑥 → ∅ ∈ 𝑥) |
4 | elom 7860 | . 2 ⊢ (∅ ∈ ω ↔ (∅ ∈ On ∧ ∀𝑥(Lim 𝑥 → ∅ ∈ 𝑥))) | |
5 | 1, 3, 4 | mpbir2an 709 | 1 ⊢ ∅ ∈ ω |
Colors of variables: wff setvar class |
Syntax hints: → wi 4 ∀wal 1539 ∈ wcel 2106 ∅c0 4322 Oncon0 6364 Lim wlim 6365 ωcom 7857 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1797 ax-4 1811 ax-5 1913 ax-6 1971 ax-7 2011 ax-8 2108 ax-9 2116 ax-ext 2703 ax-sep 5299 ax-nul 5306 ax-pr 5427 |
This theorem depends on definitions: df-bi 206 df-an 397 df-or 846 df-3or 1088 df-3an 1089 df-tru 1544 df-fal 1554 df-ex 1782 df-sb 2068 df-clab 2710 df-cleq 2724 df-clel 2810 df-ne 2941 df-ral 3062 df-rex 3071 df-rab 3433 df-v 3476 df-dif 3951 df-un 3953 df-in 3955 df-ss 3965 df-pss 3967 df-nul 4323 df-if 4529 df-pw 4604 df-sn 4629 df-pr 4631 df-op 4635 df-uni 4909 df-br 5149 df-opab 5211 df-tr 5266 df-eprel 5580 df-po 5588 df-so 5589 df-fr 5631 df-we 5633 df-ord 6367 df-on 6368 df-lim 6369 df-om 7858 |
This theorem is referenced by: onnseq 8346 rdg0 8423 fr0g 8438 seqomlem3 8454 oa1suc 8533 o2p2e4 8543 om1 8544 oe1 8546 nna0r 8611 nnm0r 8612 nnmcl 8614 nnecl 8615 nnmsucr 8627 nnaword1 8631 nnaordex 8640 1onnALT 8642 oaabs2 8650 nnm1 8653 nneob 8657 omopth 8663 snfi 9046 0fin 9173 0sdom1domALT 9241 isinf 9262 findcard2OLD 9286 nnunifi 9296 unblem2 9298 infn0 9309 infn0ALT 9310 unfilem3 9314 dffi3 9428 inf0 9618 infeq5i 9633 axinf2 9637 dfom3 9644 infdifsn 9654 noinfep 9657 cantnflt 9669 cnfcomlem 9696 cnfcom 9697 cnfcom2lem 9698 cnfcom3lem 9700 cnfcom3 9701 brttrcl2 9711 ttrcltr 9713 rnttrcl 9719 trcl 9725 rankdmr1 9798 rankeq0b 9857 cardlim 9969 infxpenc 10015 infxpenc2 10019 alephgeom 10079 alephfplem4 10104 ackbij1lem13 10229 ackbij1 10235 ackbij1b 10236 ominf4 10309 fin23lem16 10332 fin23lem31 10340 fin23lem40 10348 isf32lem9 10358 isf34lem7 10376 isf34lem6 10377 fin1a2lem6 10402 fin1a2lem7 10403 fin1a2lem11 10407 axdc3lem2 10448 axdc3lem4 10450 axdc4lem 10452 axcclem 10454 axdclem2 10517 pwfseqlem5 10660 omina 10688 wunex3 10738 1lt2pi 10902 1nn 12227 om2uzrani 13921 uzrdg0i 13928 fzennn 13937 axdc4uzlem 13952 hash1 14368 fnpr2o 17507 fvpr0o 17509 ltbwe 21818 2ndcdisj2 23181 precsexlem11 27890 0n0s 27927 snct 32193 goelel3xp 34625 satfv0 34635 satfv1 34640 satf0 34649 satf00 34651 satf0suclem 34652 sat1el2xp 34656 fmla0 34659 fmlasuc0 34661 fmla1 34664 gonan0 34669 gonar 34672 goalr 34674 satffunlem1lem2 34680 satffunlem1 34684 satefvfmla0 34695 prv0 34707 nnuni 34988 0hf 35441 neibastop2lem 35548 bj-rdg0gALT 36255 rdgeqoa 36554 exrecfnlem 36563 finxp0 36575 onexomgt 42292 onexoegt 42295 omnord1 42357 oenord1 42368 oaomoencom 42369 cantnftermord 42372 cantnfub 42373 cantnf2 42377 dflim5 42381 oacl2g 42382 onmcl 42383 omabs2 42384 omcl2 42385 tfsconcat0b 42398 ofoaf 42407 ofoafo 42408 ofoaid1 42410 ofoaid2 42411 naddcnff 42414 naddcnffo 42416 naddcnfid1 42419 naddcnfid2 42420 0finon 42501 0iscard 42594 |
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