Theorem 19.3v 1983

Description: Version of 19.3 2205 with a disjoint variable condition, requiring fewer axioms. Any formula can be universally quantified using a variable which it does not contain. See also 19.9v 1985. (Contributed by Anthony Hart, 13-Sep-2011.) Remove dependency on ax-7 2009. (Revised by Wolf Lammen, 4-Dec-2017.) (Proof shortened by Wolf Lammen, 20-Oct-2023.)

Assertion

Ref	Expression
19.3v	⊢ (∀𝑥𝜑 ↔ 𝜑)

Distinct variable group:   𝜑,𝑥

Proof of Theorem 19.3v

Step	Hyp	Ref	Expression
1		spvw 1982	. 2 ⊢ (∀𝑥𝜑 → 𝜑)
2		ax-5 1911	. 2 ⊢ (𝜑 → ∀𝑥𝜑)
3	1, 2	impbii 209	1 ⊢ (∀𝑥𝜑 ↔ 𝜑)

Syntax hints:   ↔ wb 206  ∀wal 1539

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1796  ax-4 1810  ax-5 1911  ax-6 1968

This theorem depends on definitions:  df-bi 207  df-ex 1781

This theorem is referenced by:  19.27v  1996  19.28v  1997  19.37v  1998  axrep1  5218  axrep4v  5222  axrep6OLD  5227  kmlem14  10052  zfcndrep  10502  zfcndpow  10504  zfcndac  10507  lfuhgr3  35152  bj-snsetex  36996  iooelexlt  37395  dford4  43061  relexp0eq  43733