Theorem falseral0 4469

Description: A false statement can only be true for elements of an empty set. (Contributed by AV, 30-Oct-2020.) (Proof shortened by TM, 16-Feb-2026.)

Assertion

Ref	Expression
falseral0	⊢ ((∀𝑥 ¬ 𝜑 ∧ ∀𝑥 ∈ 𝐴 𝜑) → 𝐴 = ∅)

Distinct variable group:   𝑥,𝐴

Allowed substitution hint:   𝜑(𝑥)

Proof of Theorem falseral0

Step	Hyp	Ref	Expression
1		alral 3067	. . 3 ⊢ (∀𝑥 ¬ 𝜑 → ∀𝑥 ∈ 𝐴 ¬ 𝜑)
2		pm2.21 123	. . . . 5 ⊢ (¬ 𝜑 → (𝜑 → ⊥))
3	2	ral2imi 3077	. . . 4 ⊢ (∀𝑥 ∈ 𝐴 ¬ 𝜑 → (∀𝑥 ∈ 𝐴 𝜑 → ∀𝑥 ∈ 𝐴 ⊥))
4	3	imp 406	. . 3 ⊢ ((∀𝑥 ∈ 𝐴 ¬ 𝜑 ∧ ∀𝑥 ∈ 𝐴 𝜑) → ∀𝑥 ∈ 𝐴 ⊥)
5	1, 4	sylan 581	. 2 ⊢ ((∀𝑥 ¬ 𝜑 ∧ ∀𝑥 ∈ 𝐴 𝜑) → ∀𝑥 ∈ 𝐴 ⊥)
6		fal 1556	. . 3 ⊢ ¬ ⊥
7	6	ralf0 4452	. 2 ⊢ (∀𝑥 ∈ 𝐴 ⊥ ↔ 𝐴 = ∅)
8	5, 7	sylib 218	1 ⊢ ((∀𝑥 ¬ 𝜑 ∧ ∀𝑥 ∈ 𝐴 𝜑) → 𝐴 = ∅)

Syntax hints:  ¬ wn 3   → wi 4   ∧ wa 395  ∀wal 1540   = wceq 1542  ⊥wfal 1554  ∀wral 3052  ∅c0 4287

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1797  ax-4 1811  ax-5 1912  ax-6 1969  ax-7 2010  ax-9 2124  ax-ext 2709

This theorem depends on definitions:  df-bi 207  df-an 396  df-tru 1545  df-fal 1555  df-ex 1782  df-sb 2069  df-clab 2716  df-cleq 2729  df-ral 3053  df-dif 3906  df-nul 4288

This theorem is referenced by:  uvtx01vtx  29488