The speaker of “To a Mouse” is a farmer who has accidentally destroyed a mouse’s nest while plowing his field. The event has evidently startled the mouse, and the speaker feels terrible about what he’s done. The very fact that the speaker addresses the mouse at length and tries to see the event from its perspective demonstrates his genuine compassion for this other creature. Indeed, the speaker seems to have a strong sense of kinship with animals in general. He suggests as much in lines 7–12, where he philosophizes about the cruelty involved in humans’ belief in their power over nature:

     I’m truly sorry Man’s dominion
     Has broken Nature’s social union,
     An’ justifies that ill opinion,
               Which makes thee startle,
     At me, thy poor, earth-born companion,
               An’ fellow-mortal!

In these lines, the speaker mourns how “Man’s dominion” over the earth has “broken Nature’s social union” and created antagonism between humans and other animals. He understands that such a breach justifies the mouse’s fright. Even so, he is greatly saddened that the mouse doesn’t share his sense of kinship.

Perhaps the first thing a reader notices about the speaker is his language. Specifically, he speaks the Scots dialect of English, which identifies him as Scottish. It’s significant that this particular Scottish farmer happens to be tilling his fields in 1785, since this timing was consequential in the history of Scottish agriculture. Increasingly intensive farming practices had been sweeping the countryside since the early eighteenth century. By that century’s final decades, widespread commercialization of farmland led to the displacement of thousands of farmers. The speaker of “To a Mouse” therefore finds himself at a troubling juncture, where he feels uncertain about what the future may hold. The speaker references his uncertainty about the future in lines 39–42, where he utters the following aphorism:

     The best laid schemes o’ Mice an’ Men
               Gang aft agley,
     An’ lea’e us nought but grief an’ pain,
               For promis’d joy!

Put in other words, this passage says that no matter what plans a person might make for their future, plans often go awry, turning hoped-for joy into deep-felt pain. Significantly, the speaker projects his own sense of uncertainty on to the mouse. This projection may help explain the length of his address to the mouse and the intensity of his remorse for destroying its nest.