Theorem ss0

Description: Any subset of the empty set is empty. Theorem 5 of Suppes p. 23. (Contributed by NM, 13-Aug-1994)

	Ref	Expression
Assertion	ss0	$$⊢A\subseteq \varnothing \to A=\varnothing$$

Proof

Step	Hyp	Ref	Expression
1		ss0b	$$⊢A\subseteq \varnothing \leftrightarrow A=\varnothing$$
2	1	biimpi	$$⊢A\subseteq \varnothing \to A=\varnothing$$