Emily Dickinson

Emily Dickinson's poem ("419") could be taken as about discovery. If we think of the poem as about discovery we can make some sense of the central image, darkness.

The interactions between Life and Darkness seem primary to the poem. Darkness obscures things to life, but by obscuring things it allows one to discover something not seen before.

Darkness is akin to uncertainty, as light is to certainty, and by being away from what is certain, it is possible to discover something new. The process is often difficult, often involves "larger Darknesses,"  "those evening of the brain- / When not a Moon disclose a sign- / or Star come out within" (lines 9-12).

In the above quote, light denotes guidance; it functions as a guiding light, whether or not that guiding light comes from within ("Star come out within")--we could think of this as inspiration--or from outside ("the Neighbor holds the Lamp" (line 3)). Not that the two are treated equally. It seems to me that the speaker holds inspiration above other kinds of guiding lights, because he/she uses some romantic language in his/her descriptions of those who venture into the unknown by their lonesome, referring to them as "The Bravest" (line 13).

The process of discovery is ultimately a mysterious one; that's what I get from the last stanza. The last stanza reads: 

Either the Darkness alters--
Or something in the sight
Adjusts itself to Midnight--
And Life steps almost straight. 

So either the Darkness alters to Life, or Life alters to Darkness. Either one makes sense of what was uncertain, or what was uncertain becomes less so. Or perhaps it's some of both.