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	$$⊢\underset{\_}{Ⅎ}x\left\{y|\forall x\phi \right\}$$

Proof

Step	Hyp	Ref	Expression
1		nfa1	$$⊢Ⅎx\forall x\phi$$
2	1	nfab	$$⊢\underset{\_}{Ⅎ}x\left\{y|\forall x\phi \right\}$$