Theorem modal-5 1027

Description: The analog in our "pure" predicate calculus of axiom 5 of modal logic S5.

Assertion

Ref	Expression
modal-5	|- (-. A.x -. ph -> A.x -. A.x -. ph)

Proof of Theorem modal-5

Step	Hyp	Ref	Expression
1		hbn1 1015	1 |- (-. A.x -. ph -> A.x -. A.x -. ph)

Syntax hints:  -. wn 2   -> wi 3  A.wal 954

This theorem was proved from axioms:  ax-1 4  ax-2 5  ax-3 6  ax-mp 7  ax-gen 963  ax-4 973  ax-5o 975  ax-6o 978

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