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Theorem bj-extru 31678
Description: There exists a variable such that holds; that is, there exists a variable. This corresponds under the standard translation to one of the formulations of the modal axiom (D), the other being 19.2 1842. (This is also extt 31408; propose to move to Main extt 31408 and allt 31405; relabel exiftru 1841 to exgen ? ). (Contributed by BJ, 12-May-2019.) (Proof modification is discouraged.)
Ref Expression
bj-extru 𝑥

Proof of Theorem bj-extru
StepHypRef Expression
1 tru 1478 . 2
21exiftru 1841 1 𝑥
Colors of variables: wff setvar class
Syntax hints:  wtru 1475  wex 1694
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1700  ax-4 1713  ax-6 1838
This theorem depends on definitions:  df-bi 195  df-tru 1477  df-ex 1695
This theorem is referenced by: (None)
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