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Theorem 19.2 1659
Description: Theorem 19.2 of [Margaris] p. 89. Note: This proof is very different from Margaris' because we only have Tarski's FOL axiom schemes available at this point. See the later 19.2g 1757 for a more conventional proof. (Contributed by NM, 2-Aug-2017.) (Revised by Wolf Lammen to remove dependency on ax-8, 4-Dec-2017.)
Assertion
Ref Expression
19.2 (xφxφ)

Proof of Theorem 19.2
StepHypRef Expression
1 id 19 . . 3 (φφ)
21exiftru 1657 . 2 x(φφ)
3219.35i 1601 1 (xφxφ)
Colors of variables: wff setvar class
Syntax hints:  wi 4  wal 1540  wex 1541
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-9 1654
This theorem depends on definitions:  df-bi 177  df-an 360  df-ex 1542
This theorem is referenced by:  19.8w  1660  19.39  1661  19.24  1662  19.34  1663
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