# Singleton of Empty Class is Transitive

## Example of Transitive Class

Let $\O$ denote the empty class.

Then the singleton $\set \O$ is transitive.

## Proof

There is one element of $\set \O$, and that is $\O$.

This is a subclass of $\set \O$.

That is, $\set \O$ is transitive.

$\blacksquare$