Six short lines, no punctuation, no capital letters, and yet two scenes seem to stand side by side. In the first, a crowd of doors stands open to the light. In the second, a bookseller has died of grief after losing his stock to fire. The poem never says that the two scenes belong together, which is why they keep drawing the reader in.
The title does a lot of quiet work. "Witnesses" makes us ask who is watching, and the only candidates are the doors. The phrase "a great crowd of doors" seems to echo the biblical "great cloud of witnesses," though here the crowd is made of wood and hinges rather than saints. That is an inference from the wording, but it fits: the doors are given a kind of solemn attention without being allowed to speak. They can only stand there, open, bearing what they have seen.
The central image is strange and rewarding. The doors have "open mouths for the light," so an entrance becomes a gaping, hungry, perhaps speechless mouth. Then comes the simile "like books people speak into." Ordinarily we read books, and here people speak into them, as if a book were a confessional or a listening ear. An open book, with its two leaves spread apart, also looks a little like a pair of open doors, so the comparison works visually as well as emotionally. Doors and books are both thresholds, things you pass through to somewhere else, and both depend on being opened. The poem's whole logic grows from that resemblance.
Against this the second stanza brings a sharp turn. "While" joins the two scenes in time, as though the doors stand open at the same moment the bookseller dies. The wording is oddly shaped: "the bookseller poor man" runs the nouns together, like a folk phrase or something translated. "Poor man" can mean both "pitiable" and "without money," and both senses suit someone who has lost his livelihood. "Dead of grief" is an old-fashioned idiom, and it carries a different weight from "died after the fire." The cause of death is sorrow, not flames. "Losses by fire" is flat and almost bureaucratic, like a phrase from a ledger, and that plainness makes the grief feel real. The plural "losses" suggests that more than inventory was destroyed.
The poem is built on contrasts: light and fire, openness and ruin, the living voices that speak into books and the silence of a man who will never speak again. Light enters the doors gently, while fire is the force that took the books. Judging by the imagery, we might picture doorways left standing, open to the sky, but the poem does not insist on this. It lets us imagine a burned street, or simply a metaphor for what remains after catastrophe.
The sound of the poem is subdued. There is no rhyme and no regular meter. The lines are short, running from four syllables ("is dead of grief") to seven ("their open mouths for the light"), and they fall in a loose, speech-like rhythm. The shortest line is also the most final, and its brevity makes it hit like a sentence handed down. Quieter echoes hold the lines together: the long "oo" and "or" sounds of "doors," "poor," and "for," the soft "s" of "mouths," "books," "speak," and "losses." The sibilance makes the poem sound hushed, as if it were being said in a library, or at a funeral.
What makes the poem significant is how much it gets from so little. It does not describe the fire or name a place. It trusts two images to meet in the reader's mind. The bookseller's death shows how deeply a person can be bound up with the things he keeps, and the doors, as witnesses, suggest that ordinary objects can hold memory. The poem also quietly makes the reader a witness. We stand at an open door, hear that a man has died, and are left with nothing to do but pay attention. A reader who does that has done what the title asks.