{ 1 } - tells us how we ought to live.
{ 2 } - is a logical principle.

Universalizability is a logical principle. It's about what follows from what -- and what we need to do to be consistent. It doesn't by itself tell us how we ought to live.

Universalizability says that making a moral judgment logically commits us to making similar judgments about similar cases. We contradict ourselves if we make conflicting judgments about cases we judge to be relevantly or exactly similar. Universalizability can be a useful tool in testing our consistency.