Power set

The power set, $\boxed{P(S)}$, is the set of all subsets of a set $S$. So $P(S) = \{ A | A \subseteq S \}$.

As every set $S$ will always have $\varnothing \subseteq S$ and $S\subseteq S$, then $\boxed{\varnothing \subseteq P(S)}$ and $\boxed{S\subseteq P(S)}$ will always be true.