Theorem ax10oe 1718

Description: Quantifier Substitution for existential quantifiers. Analogue to ax10o 1643 but for ∃ rather than ∀. (Contributed by Jim Kingdon, 21-Dec-2017.)

Assertion

Ref	Expression
ax10oe	⊢ (∀𝑥 𝑥 = 𝑦 → (∃𝑥𝜓 → ∃𝑦𝜓))

Proof of Theorem ax10oe

Step	Hyp	Ref	Expression
1		ax-ia3 106	. . . 4 ⊢ (𝑥 = 𝑦 → (𝜓 → (𝑥 = 𝑦 ∧ 𝜓)))
2	1	alimi 1384	. . 3 ⊢ (∀𝑥 𝑥 = 𝑦 → ∀𝑥(𝜓 → (𝑥 = 𝑦 ∧ 𝜓)))
3		exim 1530	. . 3 ⊢ (∀𝑥(𝜓 → (𝑥 = 𝑦 ∧ 𝜓)) → (∃𝑥𝜓 → ∃𝑥(𝑥 = 𝑦 ∧ 𝜓)))
4	2, 3	syl 14	. 2 ⊢ (∀𝑥 𝑥 = 𝑦 → (∃𝑥𝜓 → ∃𝑥(𝑥 = 𝑦 ∧ 𝜓)))
5		ax11e 1717	. . 3 ⊢ (𝑥 = 𝑦 → (∃𝑥(𝑥 = 𝑦 ∧ 𝜓) → ∃𝑦𝜓))
6	5	sps 1470	. 2 ⊢ (∀𝑥 𝑥 = 𝑦 → (∃𝑥(𝑥 = 𝑦 ∧ 𝜓) → ∃𝑦𝜓))
7	4, 6	syld 44	1 ⊢ (∀𝑥 𝑥 = 𝑦 → (∃𝑥𝜓 → ∃𝑦𝜓))

Syntax hints:   → wi 4   ∧ wa 102  ∀wal 1282   = wceq 1284  ∃wex 1421

This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 104  ax-ia2 105  ax-ia3 106  ax-5 1376  ax-gen 1378  ax-ie1 1422  ax-ie2 1423  ax-11 1437  ax-4 1440  ax-ial 1467

This theorem depends on definitions:  df-bi 115

This theorem is referenced by: (None)