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Theorem modal-b 1752
Description: The analog in our "pure" predicate calculus of the Brouwer axiom (B) of modal logic S5. (Contributed by NM, 5-Oct-2005.)
Assertion
Ref Expression
modal-b (φx ¬ x ¬ φ)

Proof of Theorem modal-b
StepHypRef Expression
1 ax6o 1750 . 2 x ¬ x ¬ φ → ¬ φ)
21con4i 122 1 (φx ¬ x ¬ φ)
Colors of variables: wff setvar class
Syntax hints:  ¬ wn 3  wi 4  wal 1540
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1546  ax-5 1557  ax-17 1616  ax-9 1654  ax-8 1675  ax-6 1729  ax-11 1746
This theorem depends on definitions:  df-bi 177  df-ex 1542
This theorem is referenced by: (None)
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