Theorem ssexi

Description: The subset of a set is also a set. (Contributed by NM, 9-Sep-1993)

	Ref	Expression
Hypotheses	ssexi.1	$$⊢B\in \mathrm{V}$$
	ssexi.2	$$⊢A\subseteq B$$
Assertion	ssexi	$$⊢A\in \mathrm{V}$$

Proof

Step	Hyp	Ref	Expression
1		ssexi.1	$$⊢B\in \mathrm{V}$$
2		ssexi.2	$$⊢A\subseteq B$$
3	1	ssex	$$⊢A\subseteq B\to A\in \mathrm{V}$$
4	2 3	ax-mp	$$⊢A\in \mathrm{V}$$