In this poem Dickinson constructs an idea that a soul mate is one who is bound to another in a profound and spiritual manner. If the premise is accepted that a soul mate is someone that is embedded in another, then Dickinson's characterization is a realistic one. The soul mate to another is one where there is a selection and a door that is "shut." The definitive nature of this selection is one that does become "unmoved," in that one does not waver from a soul mate. While the modern understanding of freedom and relationships could emphasize the idea of multiple partners and changing status of associations, Dickinson operates from the point of view that a soul mate is exclusive by nature. Once this is found, little can change it. This is the reasoning behind couples who have been married for over four or five decades and continue to love one another. They would embody a soul that has chosen another, remained "unmoved" to leave that mate. When this selection has been made, "the divine majority obtrude no more." It is in this light where Dickinson's construction of a soul mate is realistic in so far that one believes in the idea of a soul mate being present for individuals.
The poem does not tell us WHY she selects one person and rejects all others. Perhaps the poem is "realistic" in that some people cleave unto one person even if other people apparently have much more to offer. Once a soul has bound itself to one person, even wealthier people (in "Chariots") and "Emperors" are turned away from the soul's humble life ("low Gate"). The one she has accepted is a "divine Majority," a Majority of One., "the Chosen One."
But despite the soul's humble dwelling or humble life, she has a kind of "Divinity." And that spiritual, intangible, value out-weighs earthly values like fame and wealth and power.