1. Emily Dickinson's poem "I Dwell in Possibility" is an extended metaphor; that is, the verses all contribute to a comparison between two unlike things, a comparison that extends, or continues throughout all three stanzas. This metaphor is that the "Possibility" in which the speaker dwells is an unstated comparison for poetry. Poetry is "fairer," or more appealing, than other places to "dwell," or exist, because it contains more possibilities for expression such as imagery, rhyme, rhythm, metaphors, similes, figurative language, connotations, and sound.

The power of imagination  can certainly be better exercised in lines of poetry, or at the minimum, in figurative language which allows so many paths of thought: "More numerous windows--/Superior for Doors." With poetry--to paraphrase Robert Browning--the speaker's reach can exceed her grasp, and, as a result, expression of both the mind and the soul can be achieved.

2. Using the 10 steps of poetry, here is an analysis:

1. Title. There is no title as Emily Dickinson's poetry takes the first line as a title
2. Poet. Emily Dickinson wrote very personal verse, often with spiritual overtones on topics of life, the state of the mind, and death.
3. Structure of the Poem. This poem is written in three stanzas with Miss Dickinson's characteristic broken lines (using dashes). There are four lines each. There is no patterned rhyme scheme as the first stanza's rhyme scheme is abbc, (the last three lines do have half-rhyme with assonance /o/: Prose, Windows, Doors); the second stanza's is cded; and the third stanza's is eefg with the first two lines a half-rhyme also with the second syllable of "fairest,"-ist and -is of the word "This" in a half-rhyme. The tone of the poem is celebratory, praising the powers of poetry. In the first stanza, the meter is iambic (unstressed syllable, followed by stressed--ta DUM--in a pattern of 4= tetrameter. Such lines are in hymn meter. Then, the third line breaks this pattern. Line 5 is almost trimeter; 6 is trimeter; then, lines 7 and 8 return to hymn meter. But, as the poem progresses, the verse becomes less restricted.
4. Level of Language. As is typical of the poetry of Dickinson, the language employed is rather formal.
5. Diction. Miss Dickinson capitalizes her "loaded" words, such as "Possibility" and the metaphor of the "House" that has "numerous...Windows" and "Superior...Doors." That is, the words meant to be more metaphoric than literal are capitalized. This capitalization places importance and emphasis upon them. "Add for an everlasting Roof/The Gambrels of the Sky."
6. Literary Devices. Of course, the main literary device is metaphor which expands, just as the power of the mind expands with poetry: "The spreading wide my narrow Hands/to gather Paradise." Other devices include simile--a comparison of two unlike things using as or like: line 5: "Of Chambers as the Cedars"; metaphors, lines 11 and 12: "The spreading wide my narrow Hands," meaning the extension of her imagination and spirit to express, "to gather Paradise."
7. Patterns or Motifs. Each line is similar in length and the extended metaphor certainly unites the poem.
8. Voice of the speaker. There is an almost reverent "voice" with the hymnal rhythm and then the use of words such as "Everlasting" and "Paradise." The reader gathers that the speaker is a poet.
9. Closing lines. The last two lines are the most exalted, connoting that poetry takes one to another level, possibly that of the sublime and spiritual.
10. Theme of the poem. One theme of this poem is that of Art. The poem is ethereal and a way of reaching the spiritual realm through words. Another theme is religiosity. Miss Dickinson comes from Puritanical New England in which poetry praised God and the spiritual world. Also, Nature is certainly a realm that is spiritual, as well, elevating the human spirit to realms beyond the mundane: " Of Chambers as the Cedars" and "The Gambrels of the Sky."