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Mirrors > Home > MPE Home > Th. List > onprc | Structured version Visualization version GIF version |
Description: No set contains all ordinal numbers. Proposition 7.13 of [TakeutiZaring] p. 38, but without using the Axiom of Regularity. This is also known as the Burali-Forti paradox (remark in [Enderton] p. 194). In 1897, Cesare Burali-Forti noticed that since the "set" of all ordinal numbers is an ordinal class (ordon 7024), it must be both an element of the set of all ordinal numbers yet greater than every such element. ZF set theory resolves this paradox by not allowing the class of all ordinal numbers to be a set (so instead it is a proper class). Here we prove the denial of its existence. (Contributed by NM, 18-May-1994.) |
Ref | Expression |
---|---|
onprc | ⊢ ¬ On ∈ V |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | ordon 7024 | . . 3 ⊢ Ord On | |
2 | ordirr 5779 | . . 3 ⊢ (Ord On → ¬ On ∈ On) | |
3 | 1, 2 | ax-mp 5 | . 2 ⊢ ¬ On ∈ On |
4 | elong 5769 | . . 3 ⊢ (On ∈ V → (On ∈ On ↔ Ord On)) | |
5 | 1, 4 | mpbiri 248 | . 2 ⊢ (On ∈ V → On ∈ On) |
6 | 3, 5 | mto 188 | 1 ⊢ ¬ On ∈ V |
Colors of variables: wff setvar class |
Syntax hints: ¬ wn 3 ∈ wcel 2030 Vcvv 3231 Ord word 5760 Oncon0 5761 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1762 ax-4 1777 ax-5 1879 ax-6 1945 ax-7 1981 ax-8 2032 ax-9 2039 ax-10 2059 ax-11 2074 ax-12 2087 ax-13 2282 ax-ext 2631 ax-sep 4814 ax-nul 4822 ax-pr 4936 ax-un 6991 |
This theorem depends on definitions: df-bi 197 df-or 384 df-an 385 df-3or 1055 df-3an 1056 df-tru 1526 df-ex 1745 df-nf 1750 df-sb 1938 df-eu 2502 df-mo 2503 df-clab 2638 df-cleq 2644 df-clel 2647 df-nfc 2782 df-ne 2824 df-ral 2946 df-rex 2947 df-rab 2950 df-v 3233 df-sbc 3469 df-dif 3610 df-un 3612 df-in 3614 df-ss 3621 df-pss 3623 df-nul 3949 df-if 4120 df-sn 4211 df-pr 4213 df-tp 4215 df-op 4217 df-uni 4469 df-br 4686 df-opab 4746 df-tr 4786 df-eprel 5058 df-po 5064 df-so 5065 df-fr 5102 df-we 5104 df-ord 5764 df-on 5765 |
This theorem is referenced by: ordeleqon 7030 ssonprc 7034 sucon 7050 orduninsuc 7085 omelon2 7119 tfr2b 7537 tz7.48-3 7584 infensuc 8179 zorn2lem4 9359 noprc 32020 |
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