Basic set theory theory dealing with membership (e.g., $x \in S$), enumeration (e.g., $\{e_1, e_2, e_3\}$), containment (e.g., $A \subseteq B$), unification (e.g., $A \cup B \cup C$), intersection (e.g., $A \cap B \cap C$), subtraction (e.g., $A - B$), comprehension (e.g., $\{f(x)~|~Q(x)\}_{x \in S}$), and cardinatly (e.g., $|S|$).

In [1]:

```
import proveit
%theory
```