It is easy for us in our day and age to dismiss Dickinson's apparent obsession with death as being some kind of display of Emmeline Grangerford's mawkishness, however, reading Dickinson and exploring this central theme of her work involves an understanding of her context and in particular the way in which death was a much more intrusive presence during the life and times of Dickinson that it is for us now thanks to medical advances. Let us just remember that thanks to illnesses such as TB or consumption, people died a lot younger and children in particular had a low mortality rate compared to today. Death was an important reality and it was normal for every family to have experienced the death of at least one child, as you were lucky to make it past the age of five. Life was much more uncertain then than it is for us today, and anybody could die very rapidly from a sudden disease.
What Dickinson does in this poem and in others which focus on the topic of death is that she tries to define and explore this ultimate experience, domesticating death and, by so doing, making it an understandable phenomenon.
Modern readers are apt to comment upon the frequency with which Dickinson returns to this subject of death, but really, so was everyone else in her culture. For artists of her time, this preoccupation reflected a pervasive real-world concern. In the mid-nineteenth century death rates were high--so high that parents often gave several of their children the same name since few would survive into adulthood. She never lets us forget that in some respects life gave her short measure; and "Because I Could Not Stop for Death" is and effort to cope with her sense of privation.
Equally, traces of Puritanism tinctured the religious discourse of Dickinson's young womanhood and members of the Amherst congregation were regularly exhorted with the blood-stirring urgency of to reflect on the imminence of their own demise. The religious thought and language was important to her poetry because it comprised the semiotic system that her society employed to discuss the mysteries of life and death.
The poem, then, is the apotheosis of that distinctive Dickinson voice, "the speaking dead" offers an astonishing combination: this conventional promise of Christianity suffused with the tonalities of Gothic tradition.
Yet, the ultimate implication of this work turns precisely upon Dickinson's capacity to explode the finite boundaries that generally define our existence--immortality. As Dickinson discusses, true immorality comes from the work of art itself.
Dickinson herself said (in a conversation with Thomas Wentworth Higginson in 1870)
How do people live without any thoughts. How do they live.
Dickinson was, for all practical purposes, a recluse who rarely left her Amherst, MA home in 55-years. She spent time alone and rarely attended church (which would have played a prominent role in shaping the lives of 19th century Americans).
In this poem, Dickinson heavily sources a metaphysical style, commonly used by 17th century poets. The tendency of metaphysical poetry is a psychogical analysis of the emotions of love and religion, carrying their penchant to shock and awe to an extreme.