Dreams are weird enough as it is, but a dream within a dream? No thanks. When we see a poem with that as the title, we can't help but groan just a little bit. We expect the poem to be an account of a dream that took place within another dream, and our heads immediately start spinning. Shmoop saw Inception, and we still can't figure out what happened at the end.
The good news is that even though the title makes us think the poem is going to be a description of a dream within a dream, that's not what it is. Sigh. Of. Relief. The poem does seem a little dreamy, sure, but it's really more about a guy wrestling with the question of whether or not life is real or just an illusion—a dream within a dream. The title, then, tells us what the poem's central preoccupation is: the nature of reality, and if, and how, we can tell if everything around is real or not, especially in the face of change and loss.