The poet, who is lamenting the loss of his sense of a permanent presence which, paradoxically, his freedom was dependent on, believes Emily to be either a signifier of this presence or the actual signified. I would suggest that Shelley's history with women, a history of intense passion that eventually leads to apathy, suggests that Emily will ultimately become a meaningless signifier. But, temporarily, she is the "harmony" that brings forth a sense of permanence. In his System of Transcendental Idealism, F. W. J. Shelling writes that freedom
is the one principle on which everything is supported, and what we behold in the objective world is not anything present outside us, but merely the inner limitation of our own free activity. Being as such is merely the expression of an impeded freedom. It is our free activity, therefore, that is fettered in knowledge. But then again we should have no conception of an activity restricted, if there were not at the same time an unrestricted activity within us. This necessary coexistence of a free but limited, and illimitable activity in one and the same identical subject must, if it exists at all, be necessary, and the deduction of this necessity appertains to the higher philosophy which is both theoretical and practical at once.
If, therefore, the system of philosophy itself divides into theoretical and practical, there must be a general proof that already in its origin, and in virtue of its concept, the self cannot be restricted (albeit free) activity without being at the same time an unrestricted one, and vice versa. This proof must itself precede both theoretical and practical philosophy.
That this proof, of the simultaneous necessary coexistence of both activities in the self, is a general proof of transcendental idealism as such, will become clear from the proof itself.
The general proof of transcendental idealism will be made out solely from the proposition derived in the foregoing: Through the act of self-consciousness, the self becomes an object to itself. (35-36)
As Schelling later explains, the becoming of an object is a transference from "infinite activity" to "fixity." By the end of Epipsychidion, the poet is repairing his sense of infinity by commanding his verses to "kneel before" his "feet" (592). The poet is aware that language's limitation makes the transference from self to "other" incomplete, and it also makes him aware of his partial loss of identity, an identity which he may feel is the very transcendent entity that must be separated from the verses that he had just written. The language serves its purpose as a reaffirmation of his own identity and it may--if we so choose to use it this way--serve the reader's purpose as a signification of a personal quest that is only temporarily important, one that is to be eventually marginalized. Shelley's negative regard monogamy substantiates this interpretation.
Schelling, F. W. J. System of Transcendental Idealism. Trans. Peter Heath. Charlottesville: University P of Virginia, 1978.