By personifying his three great motivations—Love, Ambition, and Poesy—the speaker suggests that he has a close relationship with these ideas, as well as certain insights into their nature.
The three figures who appear before the speaker as he awakes one morning look "like figures on a marble Urn"—a simile that suggests they have something to do with timeless themes, ideas that have been around since ancient Greece. When they finally reveal their identities, they're indeed old as the hills:
- There's Love, of course, who turns up in the form of a beautiful girl.
- There's Ambition, who's looking pretty pale and sickly.
- And there's Poesy, a "Maiden most unmeek," bold and demanding.
These depictions reveal something about how the speaker sees his motivations—especially when he gets into his reasons for turning away from these "Shadows":
- Love might be lovely, for instance, but "where is it?" This maiden is as evasive and tricksy as she's beautiful.
- Ambition, worn out from effort and from a hunger for fame, doesn't look too good. And, as the speaker observes, Ambition is a petty thing, born of anxiety about how the "short fever-fit" of a guy's life might not amount to much.
- Poesy, finally, often fails. She gets "blame [...] heap'd upon her," attracting criticism—perhaps for bad verse, perhaps for wasted time.
The speaker is pretty quick to wash his hands of Love and Ambition (though, as the poem makes clear, he can't banish them for good). But he's more ambivalent about Poesy: he loves her all the more when people criticize her, and he admits that she does offer "joy," even if he claims to prefer the joys of indolence.
By presenting these motivations as figures he can interact with, the speaker suggests that he knows them as you'd know a person: they're his long-time companions. He also suggests that the three have a relationship with each other. After all, Love, Ambition, and Poesy walk hand in hand.