Theorem nfaba1

Description: Bound-variable hypothesis builder for a class abstraction. (Contributed by Mario Carneiro, 14-Oct-2016) Add disjoint variable condition to avoid ax-13 . See nfaba1g for a less restrictive version requiring more axioms. (Revised by Gino Giotto, 20-Jan-2024)

	Ref	Expression
Assertion	nfaba1	⊢ Ⅎ 𝑥 { 𝑦 ∣ ∀ 𝑥 𝜑 }

Proof

Step	Hyp	Ref	Expression
1		nfa1	⊢ Ⅎ 𝑥 ∀ 𝑥 𝜑
2	1	nfab	⊢ Ⅎ 𝑥 { 𝑦 ∣ ∀ 𝑥 𝜑 }