Theorem hbs1

Description: The setvar x is not free in [ y / x ] ph when x and y are distinct. (Contributed by NM, 26-May-1993)

	Ref	Expression
Assertion	hbs1	$$⊢\left[y/x\right]\phi \to \forall x\left[y/x\right]\phi$$

Proof

Step	Hyp	Ref	Expression
1		nfs1v	$$⊢Ⅎx\left[y/x\right]\phi$$
2	1	nf5ri	$$⊢\left[y/x\right]\phi \to \forall x\left[y/x\right]\phi$$