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Theorem nfnth 1679
Description: No variable is (effectively) free in a non-theorem. (Contributed by Mario Carneiro, 6-Dec-2016.)
Hypothesis
Ref Expression
nfnth.1  |-  -.  ph
Assertion
Ref Expression
nfnth  |-  F/ x ph

Proof of Theorem nfnth
StepHypRef Expression
1 nfnth.1 . . 3  |-  -.  ph
21pm2.21i 135 . 2  |-  ( ph  ->  A. x ph )
32nfi 1674 1  |-  F/ x ph
Colors of variables: wff setvar class
Syntax hints:   -. wn 3   A.wal 1442   F/wnf 1667
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1669
This theorem depends on definitions:  df-bi 189  df-nf 1668
This theorem is referenced by:  nffal  1680  nd1  9012  nd2  9013
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