Theorem hbsb2a 1684

Description: Special case of a bound-variable hypothesis builder for substitution. (Contributed by NM, 2-Feb-2007.)

Assertion

Ref	Expression
hbsb2a	⊢ ([y / x]∀yφ → ∀x[y / x]φ)

Proof of Theorem hbsb2a

Step	Hyp	Ref	Expression
1		sb4a 1679	. 2 ⊢ ([y / x]∀yφ → ∀x(x = y → φ))
2		sb2 1647	. . 3 ⊢ (∀x(x = y → φ) → [y / x]φ)
3	2	a5i 1432	. 2 ⊢ (∀x(x = y → φ) → ∀x[y / x]φ)
4	1, 3	syl 14	1 ⊢ ([y / x]∀yφ → ∀x[y / x]φ)

Syntax hints:   → wi 4  ∀wal 1240  [wsb 1642

This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 99  ax-ia2 100  ax-ia3 101  ax-5 1333  ax-gen 1335  ax-ie1 1379  ax-ie2 1380  ax-11 1394  ax-4 1397  ax-i9 1420  ax-ial 1424

This theorem depends on definitions:  df-bi 110  df-sb 1643

This theorem is referenced by:  hbsb3  1686