Theorem axrep5 5287

Description: Axiom of Replacement (similar to Axiom Rep of [BellMachover] p. 463). The antecedent tells us 𝜑 is analogous to a "function" from 𝑥 to 𝑦 (although it is not really a function since it is a wff and not a class). In the consequent we postulate the existence of a set 𝑧 that corresponds to the "image" of 𝜑 restricted to some other set 𝑤. The hypothesis says 𝑧 must not be free in 𝜑. (Contributed by NM, 26-Nov-1995.) (Revised by Mario Carneiro, 14-Oct-2016.)

Hypothesis

Ref	Expression
axrep5.1	⊢ Ⅎ𝑧𝜑

Assertion

Ref	Expression
axrep5	⊢ (∀𝑥(𝑥 ∈ 𝑤 → ∃𝑧∀𝑦(𝜑 → 𝑦 = 𝑧)) → ∃𝑧∀𝑦(𝑦 ∈ 𝑧 ↔ ∃𝑥(𝑥 ∈ 𝑤 ∧ 𝜑)))

Distinct variable group:   𝑥,𝑦,𝑧,𝑤

Allowed substitution hints:   𝜑(𝑥,𝑦,𝑧,𝑤)

Proof of Theorem axrep5

Step	Hyp	Ref	Expression
1		19.37v 1991	. . . . 5 ⊢ (∃𝑧(𝑥 ∈ 𝑤 → ∀𝑦(𝜑 → 𝑦 = 𝑧)) ↔ (𝑥 ∈ 𝑤 → ∃𝑧∀𝑦(𝜑 → 𝑦 = 𝑧)))
2		impexp 450	. . . . . . . 8 ⊢ (((𝑥 ∈ 𝑤 ∧ 𝜑) → 𝑦 = 𝑧) ↔ (𝑥 ∈ 𝑤 → (𝜑 → 𝑦 = 𝑧)))
3	2	albii 1819	. . . . . . 7 ⊢ (∀𝑦((𝑥 ∈ 𝑤 ∧ 𝜑) → 𝑦 = 𝑧) ↔ ∀𝑦(𝑥 ∈ 𝑤 → (𝜑 → 𝑦 = 𝑧)))
4		19.21v 1939	. . . . . . 7 ⊢ (∀𝑦(𝑥 ∈ 𝑤 → (𝜑 → 𝑦 = 𝑧)) ↔ (𝑥 ∈ 𝑤 → ∀𝑦(𝜑 → 𝑦 = 𝑧)))
5	3, 4	bitr2i 276	. . . . . 6 ⊢ ((𝑥 ∈ 𝑤 → ∀𝑦(𝜑 → 𝑦 = 𝑧)) ↔ ∀𝑦((𝑥 ∈ 𝑤 ∧ 𝜑) → 𝑦 = 𝑧))
6	5	exbii 1848	. . . . 5 ⊢ (∃𝑧(𝑥 ∈ 𝑤 → ∀𝑦(𝜑 → 𝑦 = 𝑧)) ↔ ∃𝑧∀𝑦((𝑥 ∈ 𝑤 ∧ 𝜑) → 𝑦 = 𝑧))
7	1, 6	bitr3i 277	. . . 4 ⊢ ((𝑥 ∈ 𝑤 → ∃𝑧∀𝑦(𝜑 → 𝑦 = 𝑧)) ↔ ∃𝑧∀𝑦((𝑥 ∈ 𝑤 ∧ 𝜑) → 𝑦 = 𝑧))
8	7	albii 1819	. . 3 ⊢ (∀𝑥(𝑥 ∈ 𝑤 → ∃𝑧∀𝑦(𝜑 → 𝑦 = 𝑧)) ↔ ∀𝑥∃𝑧∀𝑦((𝑥 ∈ 𝑤 ∧ 𝜑) → 𝑦 = 𝑧))
9		nfv 1914	. . . . 5 ⊢ Ⅎ𝑧 𝑥 ∈ 𝑤
10		axrep5.1	. . . . 5 ⊢ Ⅎ𝑧𝜑
11	9, 10	nfan 1899	. . . 4 ⊢ Ⅎ𝑧(𝑥 ∈ 𝑤 ∧ 𝜑)
12	11	axrep4 5285	. . 3 ⊢ (∀𝑥∃𝑧∀𝑦((𝑥 ∈ 𝑤 ∧ 𝜑) → 𝑦 = 𝑧) → ∃𝑧∀𝑦(𝑦 ∈ 𝑧 ↔ ∃𝑥(𝑥 ∈ 𝑤 ∧ (𝑥 ∈ 𝑤 ∧ 𝜑))))
13	8, 12	sylbi 217	. 2 ⊢ (∀𝑥(𝑥 ∈ 𝑤 → ∃𝑧∀𝑦(𝜑 → 𝑦 = 𝑧)) → ∃𝑧∀𝑦(𝑦 ∈ 𝑧 ↔ ∃𝑥(𝑥 ∈ 𝑤 ∧ (𝑥 ∈ 𝑤 ∧ 𝜑))))
14		anabs5 663	. . . . . 6 ⊢ ((𝑥 ∈ 𝑤 ∧ (𝑥 ∈ 𝑤 ∧ 𝜑)) ↔ (𝑥 ∈ 𝑤 ∧ 𝜑))
15	14	exbii 1848	. . . . 5 ⊢ (∃𝑥(𝑥 ∈ 𝑤 ∧ (𝑥 ∈ 𝑤 ∧ 𝜑)) ↔ ∃𝑥(𝑥 ∈ 𝑤 ∧ 𝜑))
16	15	bibi2i 337	. . . 4 ⊢ ((𝑦 ∈ 𝑧 ↔ ∃𝑥(𝑥 ∈ 𝑤 ∧ (𝑥 ∈ 𝑤 ∧ 𝜑))) ↔ (𝑦 ∈ 𝑧 ↔ ∃𝑥(𝑥 ∈ 𝑤 ∧ 𝜑)))
17	16	albii 1819	. . 3 ⊢ (∀𝑦(𝑦 ∈ 𝑧 ↔ ∃𝑥(𝑥 ∈ 𝑤 ∧ (𝑥 ∈ 𝑤 ∧ 𝜑))) ↔ ∀𝑦(𝑦 ∈ 𝑧 ↔ ∃𝑥(𝑥 ∈ 𝑤 ∧ 𝜑)))
18	17	exbii 1848	. 2 ⊢ (∃𝑧∀𝑦(𝑦 ∈ 𝑧 ↔ ∃𝑥(𝑥 ∈ 𝑤 ∧ (𝑥 ∈ 𝑤 ∧ 𝜑))) ↔ ∃𝑧∀𝑦(𝑦 ∈ 𝑧 ↔ ∃𝑥(𝑥 ∈ 𝑤 ∧ 𝜑)))
19	13, 18	sylib 218	1 ⊢ (∀𝑥(𝑥 ∈ 𝑤 → ∃𝑧∀𝑦(𝜑 → 𝑦 = 𝑧)) → ∃𝑧∀𝑦(𝑦 ∈ 𝑧 ↔ ∃𝑥(𝑥 ∈ 𝑤 ∧ 𝜑)))

Syntax hints:   → wi 4   ↔ wb 206   ∧ wa 395  ∀wal 1538  ∃wex 1779  Ⅎwnf 1783

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1795  ax-4 1809  ax-5 1910  ax-6 1967  ax-7 2007  ax-12 2177  ax-rep 5279

This theorem depends on definitions:  df-bi 207  df-an 396  df-or 849  df-tru 1543  df-ex 1780  df-nf 1784

This theorem is referenced by:  zfrepclf  5291