Sixteen words, and the first two lines already pose a puzzle: who are "Her sovereign People," and who is "Her"? Dickinson turns the sentence inside out, so the answer arrives only once we reach line two. Put back in ordinary order, it reads: Nature knows her sovereign People as well, and is as fond of signifying them, as if she were fallible. By opening with the object, Dickinson works like a herald announcing the title before the person walks in.
The poem never says who these sovereign People are. The capital P suggests something grand, perhaps the finest of Nature's creatures, perhaps people of unusual worth, but the text leaves the choice to us. The phrase itself is a small paradox. "Sovereign" points to one ruler above everyone else, while "People" points to the many. Readers in a republic may also hear the familiar idea that the people hold the power. Either way, Nature has a court, and she knows exactly who belongs in it.
The real subject of the poem is how Nature behaves toward them. Knowing something is private, but "signifying" is public: it means marking, pointing out, giving a sign. Nature does more than recognise her favourites. She likes to make a show of them, the way a ceremony sorts out ranks and titles. Then comes the sly final clause. Nature is not fallible, so she has no reason to label anyone, yet she does it with the eagerness of someone who might get it wrong. The joke is that an all-knowing power acts like a status-conscious human. The clause can be read another way, as Nature double-checking herself as if she could err, but both readings give the same picture of the infinite behaving with human fussiness.
The word "fond" helps this along. It belongs to grandparents and pet owners, not to goddesses, so it brings Nature's power down to the scale of ordinary affection. Her "sovereign People" are being doted on, and a little showing-off comes with the dotage.
The form supports the idea. The lines are short, short, long, short. If "sovereign" is said in two syllables, the count runs roughly five, five, nine, five. Lines one, two and four move briskly, with two or three strong beats each. Line three stretches out, with "signifying" taking up much of the space. It is also the longest, most Latinate word in a poem otherwise built from plain short ones, so it carries a faint pomp, as if the line were putting on ceremonial dress. Then the poem snaps back to a four-syllable close, and the grandeur deflates with it.
The rhyme is just as restrained. Lines one and three do not rhyme at all. Lines two and four, "well" and "fallible," share only a closing l sound, a near-rhyme that does not quite click shut. A perfect rhyme would suit infallible Nature, so the imperfect one quietly matches the "as if fallible" of the last line. The final line also has no verb. "As if fallible" leaves out "she were," a typical Dickinson compression that makes the reader fill the gap. The dash that ends the poem keeps the thought open instead of closing it with a full stop, so the poem trails away.
This tiny poem shows several of Dickinson's habits. She lived in Amherst, Massachusetts, wrote mostly in short compressed forms, and filled her lines with dashes and capitalised nouns, and most of her poems were not published in her lifetime. Here those habits create an effect larger than the word count. Nature appears as a character with a personality, and the poem treats rank, recognition and pride, all very human concerns, with gentle mockery. The grammar makes us work to find out who is speaking and who is being honoured, and the closing word reminds us that the one being teased is the one who cannot make mistakes. In so few words, Dickinson makes the natural world look like an anxious court.