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Mirrors > Home > ILE Home > Th. List > snprc | Unicode version |
Description: The singleton of a proper class (one that doesn't exist) is the empty set. Theorem 7.2 of [Quine] p. 48. (Contributed by NM, 5-Aug-1993.) |
Ref | Expression |
---|---|
snprc |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | velsn 3587 | . . . 4 | |
2 | 1 | exbii 1592 | . . 3 |
3 | 2 | notbii 658 | . 2 |
4 | eq0 3422 | . . 3 | |
5 | alnex 1486 | . . 3 | |
6 | 4, 5 | bitri 183 | . 2 |
7 | isset 2727 | . . 3 | |
8 | 7 | notbii 658 | . 2 |
9 | 3, 6, 8 | 3bitr4ri 212 | 1 |
Colors of variables: wff set class |
Syntax hints: wn 3 wb 104 wal 1340 wceq 1342 wex 1479 wcel 2135 cvv 2721 c0 3404 csn 3570 |
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 604 ax-in2 605 ax-io 699 ax-5 1434 ax-7 1435 ax-gen 1436 ax-ie1 1480 ax-ie2 1481 ax-8 1491 ax-10 1492 ax-11 1493 ax-i12 1494 ax-bndl 1496 ax-4 1497 ax-17 1513 ax-i9 1517 ax-ial 1521 ax-i5r 1522 ax-ext 2146 |
This theorem depends on definitions: df-bi 116 df-tru 1345 df-fal 1348 df-nf 1448 df-sb 1750 df-clab 2151 df-cleq 2157 df-clel 2160 df-nfc 2295 df-v 2723 df-dif 3113 df-nul 3405 df-sn 3576 |
This theorem is referenced by: prprc1 3678 prprc 3680 snexprc 4159 sucprc 4384 snnen2oprc 6817 unsnfidcex 6876 |
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