The poem’s metaphors transform the speaker’s philosophies into concrete, surprising, and even funny images.
In the second stanza, the speaker personifies the qualities that make his garden perfect, presenting “Quiet” and “Innocence” as a pair of lovely sisters. There’s something ironic about this moment: the only reason Quiet and Innocence live in the garden is because there’s nobody there! The only company the speaker needs, the personification suggests, is the absence of company.
Company, after all, only leads to struggles and troubles. The speaker is particularly happy to leave behind the exhausting pursuit of romance. Lovers, he observes, become “cruel as their flame”—that is, cruel as the metaphorical flame of passion that burns within them. Such flames drive them to do silly things like carve their beloveds’ names on the bark of innocent trees, behavior the speaker rolls his eyes over.
He's far happier spending his time in:
The mind, that ocean where each kind
Does straight its own resemblance find;
This metaphor draws on the old belief that the ocean contains an analogue of every land animal: if there are rabbits on land, for instance, there must be sea-rabbits to match them. If the mind is an ocean, it’s not only vast and deep but also a mirror of the whole world, inhabited by a mind-copy of everything it observes around it.
Navigating this inner ocean, the speaker can get so absorbed in his imagination that he feels as if he’s tossed “the body’s vest aside”—that is, as if he’s shrugged off his body like an old jacket. His soul, in a simile, is then “like a bird,” unbound from earthly limitations and free to fly among the green branches above him.
Above and around all these metaphors, some might read the speaker’s dazzlingly green garden as itself a conceit, an extended metaphor for the poet’s own mind. This solitary place, after all, is endlessly lush, sensuous, and creatively fertile, just like the generative imagination the speaker describes in the sixth stanza.