A Death blow is a Life blow to Some
Who till they died, did not alive become--
Who had they lived-- had died but when
They died, Vitality begun--
This poem seems to be a paradox in its assertion that death can produce life. At times it is a paradox, and Dickinson weilds this literary technique with great precision. Much of the poem is constructed of parallel statements, ironic and exacting. Not only does life exist in death, but death has existed in life. I feel like this concept-- life in death and death in life-- is one of the easier recurring themes in Dickinson's poetry that is easier for people in the current era to understand. We have seen people who are slaves to their circumstances, who exist merely to exist, who have no purpose or aim, who barely scrape by. The art and music world are full of this theme, including songs like the recently popular country song "Live Like You Were Dying" by Tim McGraw.
And yet, I'm not sure that Dickinson's poem means that until we face the reality of death that we cannot live. Given her frequent use of death in her poetry, as both theme and character, I wonder if this poem doesn't refer to life after death-- one that can be richer and far more extensive than the limited lives she often incorporates into her poetry. Perhaps the eternal soul-- or possibly more accurate to Dickinson would be the written word-- is the "Vitality begun" in the final line. In many ways, Dickinson's life can almost be seen as a death, and her death and its subsequent discovery of her writings as a new "vitality."
Perhaps it could also refer to the life that can grow out the death of other things. In this approach to the poem, one could draw a parallel to T.S. Elliot's "The Waste Land" with it's opening lines: "April is the cruellest month, breeding / Lilacs out of the dead land, mixing / Memory and desire, stirring / Down dull roots with spring rain." The spring taunts those who are dead inside, mocking those with no inner life with its vitality. Similarly, in Dickinson's poem the speaker could be trying to make the point that everything is a matter of perspective. Therefore, what is a death blow to one might very well be a life blow to another, shocking the person not into destruction but into new vigor.