The speaker is a woman of mystery. In fact, she's so mysterious that she never even tells us if she's a "she." We just call her "she" because saying "he or she" the whole time is mad clunky. Even though the speaker never tells us who she is or where she's from, we can definitely make a few assumptions about the sorts of things she's experienced in life.
For one, we can probably assume that she's gone through some kind of serious trauma. The poem describes in such detail the complex feelings that wash over somebody in the aftermath of a traumatic event, that we figure there's a high probability that the speaker has firsthand experience. We mean, just look at how complex this second stanza is:
The Feet, mechanical, go round –
A Wooden way
Of Ground, or Air, or Ought –
A Quartz contentment, like a stone – (5-9)
All this vivid, but fractured imagery—it so clearly gives a peek inside the head of somebody who's numb and confused. The speaker is obviously a deep thinker, who's in touch with her emotions; she's unafraid to dig into all the contradictions that bubble up inside us when we're in shock.
We never know exactly what kind of trauma the speaker has experienced. All the deathly imagery, like the "Tombs" in 1.2, hint that it might be the death of a loved one, but we never know for sure. The speaker only digs into the emotion (or lack there of) that comes after. It's cool because it allows us to easily apply this to our own lives. Wait. So does that mean that we're all the speaker in a way?
Whoa, our minds are blown.