Sparknotes translates Dickinson's poem as:
“[It's about] the mind’s capacity to absorb, interpret, and subsume perception and experience.
The brain is wider than the sky despite the sky’s awesome size
because the brain is able to incorporate the universe into itself,
and thereby even to absorb the ocean.
The source of this capacity, in this poem, is God.”
Over the course of hundreds of millions of years, it evolved tailored by the environment, and we developed handy tools like feelings, learning, and memory.
"During the last 30 thousand years (at least), the human species has incessantly questioned its own nature and it's position within the universe—an overwhelmingly empty enterprise because of the paucity of valid answers and always led by a search for religious meaning.
Little by little, this search has been stripped of its divine sense as attitudes evolved through the influence of the scientific community and by the transformation of societies in modern nation-states.
Thus, a huge role has been played by scientists:
- Copernicus and Galileo showed that we are not the center of the universe,
- Darwin recognized the animal with our being,
- Freud placed consciousness at the center of the scientific quest,
- and Einstein equated matter with energy and showed nature's dependence on point of view."
It's all about perspective.
And the evolution of not only our brains, but of our shared experience.
I very much respect Dickinson for expressing her inner reflections via poetry, like past poets Rumi and 寒山.
In Dickinson's opinion, the mind is a manifestation of God, or the individual is an instrument of God.
[here's a little poem response dedicated to her]
you may be wider than the sky...
for total absorption
resist the ocean's deafening roar
participate with silence
the love within
our own reflection(s).