I dwell in Possibility —
A fairer House than Prose —
More numerous of Windows —
Superior — for Doors —
Of Chambers as the Cedars —
Impregnable of eye —
And for an everlasting Roof
The Gambrels of the Sky —
Of Visitors — the fairest —
For Occupation — This —
The spreading wide my narrow Hands
To gather Paradise —
Dickinson chooses the word "dwell." She doesn't write "I live in Possibility," or "Possibility is my home." She writes: "I dwell in possibility." The words "dwell" and "live" both have to do with residence, but one is definitely more passive-sounding than the other. To dwell somewhere--this is a place you choose to stay in. Note the origins of the word: Old English dwellan meaning 'lead astray, hinder, delay' (in Middle English 'tarry, remain in a place'). To dwell upon something means to linger, to stop and think for a while.
There's definitely more packed meaning in that one word, and it's directly related to that site of "Possibility," isn't it? What do we dwell upon? Shallow things? No, we dwell upon something because there's a well of meaning, a well of knowledge we may not have encountered before. And for her, poetry is this well.