Thanks, Vishul! A really annoying fact about MathJax on this website is that braces don't work:

`\\( \{x,y\} \\)`

delivers

\\( \{x,y\} \\)

So, I retyped your comment using a hack. This was a bit tiring given the nested braces! I typed

> `There are exactly two partitions of the two-element set {\\(\bullet,\ast\\)}, _viz._
> {{\\(\bullet, \ast\\)}}, and {{\\(\bullet\\)}, {\\(\ast\\)}}.`

and got

> There are exactly two partitions of the two-element set {\\(\bullet,\ast\\)}, _viz._ {{\\(\bullet, \ast\\)}}, and {{\\(\bullet\\)}, {\\(\ast\\)}}.

I'm glad we're doing category theory and not set theory!