1. Nothing that has its thorn could be anything other than a rose.
2. Nothing that has its dawn could be anything other than a night.
3. Nothing that sings a sad, sad song could be anything other than a cowboy.
4. Everything that lacks its dawn and doesn't sing a sad, sad song is a rose.
5. Every night lacking its thorn sings a sad, sad song.
6. No cowboy lacking its dawn has its thorn.
7. No rose that doesn't sing a sad, sad song has its dawn.
8. No rose that is not also a night is a cowboy.

Every rose has its thorn.
Every night has its dawn.
Every cowboy sings a sad, sad song.
All of the above.
None of the above.