Eight short lines, one question and one answer: Dickinson packs a whole argument about why suffering exists into a space smaller than most text messages. The poem begins with an odd, slightly alarming picture. A "Tooth" sits "upon Our Peace." It is not clear whether it bites or merely rests there, but either way something sharp has been placed against something calm. The speaker doesn't panic. She notes that the Peace "cannot deface" the Tooth, or rather that the Tooth cannot deface the Peace. The syntax lets the two be read in either direction, which suits a poem about opposites that cannot be separated. Then comes the child-like challenge: "Then Wherefore be the Tooth?" If it can't even leave a mark, what is it for?
The answer is "To vitalize the Grace." The verb is the surprise. A tooth ought to destroy, yet this one gives life. The idea is that peace which has never been pricked would be numb, hardly noticeable. Grace becomes vivid only against something that threatens it. "Deface" is a precise choice here. It means to spoil a surface, and the poem imagines a pain that touches the surface of peace without ruining it, like a pressure that makes you aware of your own skin.
The second stanza widens the claim from private feeling to cosmic design. "The Heaven hath a Hell," and the reason given is neither punishment nor justice. Hell exists "Itself to signalize," so that Heaven can mark itself out and be recognised. The archaic "hath" gives the line the sound of doctrine, but the logic is almost that of a designer. A thing needs a contrast to be seen at all. The final image is the strangest: "every sign before the Place / Is Gilt with Sacrifice." The signposts leading toward Heaven are coated in gold, and what makes them glitter is sacrifice. The vocabulary of Grace, Heaven, Hell and Sacrifice is that of Christian theology, though the poem never names a doctrine or a story. "Gilt" also sounds like "guilt," and it is tempting to hear that second word underneath. That is a reading, not something the poem states, but it adds a shadow to the shine. Gold laid over a surface can suggest real value or a pleasant cover for something painful.
The form is as compact as the thought. The lines are mostly six syllables, light and quick, and the hymn-like rhythm gives the argument a confidence that the questioning tone half-undermines. In the second stanza the third line stretches to eight syllables ("And every sign before the Place"), as if the poem slows to look down the road toward its destination. The rhyme is partial and slightly off-kilter. "Deface" and "Grace" match properly, but "signalize" and "Sacrifice" only nearly meet. The long *-ace* sound also runs through the whole poem, from "Peace" and "deface" to "Grace" and "Place," so that the key words echo one another. Peace, grace and place end up sounding like members of one family, and the Tooth ("Tooth," "Hell") is the sharp outsider that interrupts the pattern at the start of lines 1 and 3.
Dickinson, who lived in Amherst, Massachusetts, and left most of her poems unpublished in her lifetime, often worked in compressed hymn-like stanzas like these, and the odd capitals and dashes here are typical of her page. The poem's significance lies in what she does with that familiar form. She takes a comforting religious idea, that suffering has a purpose, and states it so briskly that it becomes unsettling. The answer arrives almost too neatly, and the reader is left to wonder whether the "Tooth" is truly justified or only explained. The poem seems to accept the idea while keeping its edge, and that is the source of its force.