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Theorem filn0 21713
 Description: The empty set is not a filter. Remark below def. 1 of [BourbakiTop1] p. I.36. (Contributed by FL, 30-Oct-2007.) (Revised by Stefan O'Rear, 28-Jul-2015.)
Assertion
Ref Expression
filn0 (𝐹 ∈ (Fil‘𝑋) → 𝐹 ≠ ∅)

Proof of Theorem filn0
StepHypRef Expression
1 filtop 21706 . 2 (𝐹 ∈ (Fil‘𝑋) → 𝑋𝐹)
2 ne0i 3954 . 2 (𝑋𝐹𝐹 ≠ ∅)
31, 2syl 17 1 (𝐹 ∈ (Fil‘𝑋) → 𝐹 ≠ ∅)
 Colors of variables: wff setvar class Syntax hints:   → wi 4   ∈ wcel 2030   ≠ wne 2823  ∅c0 3948  ‘cfv 5926  Filcfil 21696 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-pow 4873  ax-pr 4936 This theorem depends on definitions:  df-bi 197  df-or 384  df-an 385  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-nel 2927  df-ral 2946  df-rex 2947  df-rab 2950  df-v 3233  df-sbc 3469  df-csb 3567  df-dif 3610  df-un 3612  df-in 3614  df-ss 3621  df-nul 3949  df-if 4120  df-pw 4193  df-sn 4211  df-pr 4213  df-op 4217  df-uni 4469  df-br 4686  df-opab 4746  df-mpt 4763  df-id 5053  df-xp 5149  df-rel 5150  df-cnv 5151  df-co 5152  df-dm 5153  df-rn 5154  df-res 5155  df-ima 5156  df-iota 5889  df-fun 5928  df-fv 5934  df-fbas 19791  df-fil 21697 This theorem is referenced by:  ufileu  21770  filufint  21771  uffixfr  21774  uffix2  21775  uffixsn  21776  hausflim  21832  fclsval  21859  isfcls  21860  fclsopn  21865  fclsfnflim  21878  filnetlem4  32501
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