How would you write a critical analysis of the "little horse" theme?

An exploration of the little horse theme must begin with considering why Robert Frost described the poem as being "about the snowy evening and the little horse." One would think the idea for the poem might be described as "about the snowy evening and the man" or "about the snowy woods and the man." The only conclusion is that, for Frost, the little horse of the poem played a significant thematic role and that its interaction with the snowy evening is perhaps as significant as the man's interaction with the "woods" as they "fill up with snow." To start an exploration of the little horse theme, we might ask what role the little horse plays in the narrative of the poem.
THE ROLE OF THE LITTLE HORSE IN THE NARRATIVE
My little horse must think it queer
To stop without a farmhouse near
Between the woods and frozen lake
The darkest evening of the year.

He gives his harness bells a shake
To ask if there is some mistake.
The only other sound’s the sweep
Of easy wind and downy flake.
The role of the little horse occupies two out of four stanzas. The little horse fills the heart of the poem in stanzas two and three. The stanza preceding the introduction of the little horse focuses on the suggested but ill-defined relationship between the man and the owner of the woods. Mention of the owner's house in the village introduces implied relationships on a wider scale.
Whose woods these are I think I know.
His house is in the village though;
He will not see me stopping here
To watch his woods fill up with snow.
Stanza four, following the action of the little horse, focuses, for the first time, on the man and introduces his promises, journey and approaching repose in sleep. [There is nothing in the tone, symbolism, or themes that suggest Frost intends "sleep" to equate to death; all point to "sleep" being the refreshing repose at the end of a day of labor and kept promises.]
The woods are lovely, dark and deep,
But I have promises to keep,
And miles to go before I sleep,
And miles to go before I sleep.
The stanza subjects introduce the theme of respected friendship through the owner of the woods in stanza one; the theme of community through the anthropomorphized little horse in stanzas two and three; and the theme of personal thoughts, obligations and actions (and their implied rewards) through the man in stanza four.
Narrative of the Poem
The narrative of the poem progresses this way. Beginning with only a vaguely suggested backstory, the man is journeying homeward on a snowy evening, on the winter solstice, when he is entranced by woods filling with woods. He and his little horse stop. He watches in mesmerized wonder, as one might easily do on a snowy evening, as the woods fill with snow. He muses to himself that he knows the owner of the lovely woods and envisions the owner watching him if he were nearby rather than living in the village. The man acknowledges that the owner will not watch him stopping before the woods because his house is not a nearby farmhouse but a house in the circle of warmth and sociability of the village. It is important to note that there is no fierce storm; no winds roar, no slanting snow pelts, no blinding sheets of snow obscure vision. It is only a snowfall on a snowy evening; not at night, but in the evening.
The little horse, having been directed to stop en route between "the woods" and "frozen lake" without a "farmhouse near," shakes his "harness bells," which sends his mane a-flying too. The man, in an implied warmth of feeling for his trusted little horse, thinks that he understands the horse's shaking head, mane, harness and bells. He interprets the little horse's action to be the result of puzzlement about their stopping by a woods instead of by a farmhouse; the little horse realizes the absence of the structures of community and fellowship. The man interprets the shaking harness bells as a question about a mistake having been made. This dramatizes the unstated promise made by the little horse to the man to get him where he needs to go in safety and in good time. A stop by woods filling with snow is a surprising diversion from their regular fulfillment of exchanged promises: The little horse promises to get the man safely where he needs to go, and the man promises to care for and protect the little horse.
Analyzing the Important Features of the Narrative
While it was not important to Frost's narrative to explain much about the man, it was important to explain in stanzas two and three rather a lot about the little horse, even if the explanation comes through the man's interpretations of its behavior. It was also important to Frost to explain at the end of stanza three quite a lot about the snowy evening. It should be noted that it is not a storm; it is simply snowing. The snow is accompanied by an "easy wind" that sweeps mildly over little horse, snow, woods, and man. The sound of the snow and wind together is "the sweep / Of easy wind and downy flake." The little horse and snowy evening are brought together when the little horse breaks the quietude of "easy wind and downy flake" by the shake of his head and "harness bells."
Stanza four focuses upon the man, revealing his thoughts, obligations, journey, and day's goal. Stanza one tells his thoughts about the ownership of the woods. Stanzas two and three tell his thoughts about the little horse's actions. Then stanza four tells his personal thoughts about what he is gazing upon. His thoughts are that the woods he gazes upon are lovely, with the dual attributes of being both dark and deep.
In truth, the snowy evening and the little horse receive most of the poetic attention. The snowy evening and the little horse together point to the man's personal thoughts in stanza four. All elements are framed by stanza one in the implied community surrounding the man and little horse. The narrative points to the expression of Frost's primary theme about the man's role/ position in his community, a community that extends to:
the absent owner,
the unnamed people of the village,
the diligent little horse
all those to whom promises are made: "But I have promises to keep, / And miles to go before I sleep"
Characteristics of the Little Horse
It communicates with the man, while the man anthropomorphizes its actions into thoughts.
It redirects the man's thoughts to their uncompleted journey.
Its interpreted thoughts remind the man that they have matters at hand to attend to that don't include mistaken stops at commonplace snowy woods.
It makes a cheerful, friendly noise in the midst of the hush of the snowfall.
What the Little Horse Accomplishes in "Stopping by Woods"
What does Frost accomplish with the characteristics of the little horse?
Frost separates the contemplative nature of the man from the practical nature of the horse.
The little horse reminds the man of the cheerful nature of practical life when he would rather get psychologically absorbed in the hush of reverie, like the hush of the wind and snowflakes.
It reminds the man of the friendliness of relationships, which are contrasted to the impersonal quality of snowy woods.
The little horse epitomizes the theme of community. This is the greatest importance of the little horse to Frost's idea and to "Stopping by Woods on a Snowy Evening."
LITTLE HORSE THEME
The little horse represents Frost's understanding and vision of community. This analysis is confirmed in "New Hampshire," the poem Frost completed immediately before writing "Stopping by Woods." In "New Hampshire" Frost describes of New Hampshire, the state where he had owned two farms, although he was living on his farm in Vermont when he wrote "New Hampshire" and "Stopping by Woods": "Anything I can say about New Hampshire / Will serve almost as well about Vermont,...." Of the New Hampshire community, he writes:
I hadn't an illusion in my hand-bag
About the people being better there
Than those I left behind. I thought they weren't.
I thought they couldn't be. And yet they were.
I'd sure had no such friends in Massachusetts
As Hall of Windham, Gay of Atkinson,
Bartlett of Raymond (now of Colorado),
Harris of Derry, and Lynch of Bethlehem ("New Hampshire," Frost).
In "Stopping by Woods," Frost extends the idea of community he was speaking of in "New Hampshire" to include the little horse upon which the man depends for safe transportation through rural elements. The exchanges between man and horse that Frost constructs--those being the man's interpretation of the little horse's thoughts, the horse's action, the man's understanding of that action--create a connectedness between man and horse. Theirs is a community in the same sense that the absent woods owner and the implied village inhabitants are a community connected with the man.
Why does Frost symbolize community with the little horse? "Little" is a a term of affection and endearment using the diminutive. "Little" associates the man's feelings for the horse with the theme of caring and safety, with not traveling miles and miles alone on snowy evenings, be they real or metaphorical. The diminutive "little" renders the horse charming and personable. Compare "little horse" to "sturdy horse" or "stallion horse" or "work horse." Each has a connotation that exerts an influence on how interaction with the man will be understood. For instance, a "sturdy" horse shaking its harness and bells might be understood as exerting dominance, "We go now." In contrast, a "little horse" is understood as friendly to the man and as making a serviceable comment with its shaking "harness bells."
Frost seems to have chosen the "little horse" to symbolize community, as well as the absent owner of the woods, in order to present the "miles to go" and "promises to keep" in a friendly light; to present them as being lovingly traveled, made, and kept, not coerced or begrudged; to present them as winsome in the same way the little horse is winsome and a pleasure. It is difficult to think of a representative individual who might facilitate that symbolism as well and thoroughly as the little horse does. The owner, absent from the scene and away in the village, expands the symbol of community without adding dominance, superiority, or other shades of meaning that might change the promises from voluntary, loving, winsome, and pleasurable to enforced or manipulated.
The theme of the little horse is that of community, and Frost defines community--through the little horse and the absent owner and villagers--as those with whom space is shared in those "miles to go" and those with whom promises, implied or explicit, are exchanged and those for whom warmth of feeling is present, as between man and little horse. In the endearing diminutive "little horse," there is also the suggestion that the man has a responsibility to make and keep promises to those who are, in some way or another, less able or more reliant upon the shared efforts of others: The little horse may take the man safely through the snowy woods, but the little horse relies upon the man to prepare and provide its oats. They share a community built upon promises made and kept.