Pope gives Mrs Corbet ten lines, and he spends most of them telling us what she was not. She wanted no "conquests" except over herself. She tried no "arts" except the art of not being admired. "Passion and pride" were "unknown" to her. The portrait is built from absences, which suits a woman whose chief virtue, in the poem's account, was refusing to show off.
The form is the heroic couplet, five pairs of rhymed iambic pentameter lines, the verse form Pope is famous for. Each couplet closes like a small door: *pretence / sense*, *desired / admired*, *unknown / own*, *mind / refined*, *tried / died*. Each pair delivers one complete judgement, which gives the poem the carved, final feel of an inscription. The vocabulary is just as sober as the woman it describes. "Plain reason" and "sober sense" are deliberately unglamorous phrases, and the opening lines avoid any display of their own. Line 4 is the cleverest of them. "No arts essay'd, but not to be admired" is a small paradox, because the poem admires her openly for the very thing she never tried to earn.
Line 6 offers the poem's one general maxim: "virtue only is our own." Beauty, health and reputation can all be taken from us, the line suggests, but virtue is the one thing we truly possess. It sounds consoling, and it quietly sets up what follows, since the poem is about to show how much else was taken from her.
The next couplet drops the verbs altogether and becomes a list of admiration: "So unaffected, so composed a mind; / So firm, yet soft; so strong, yet so refined." The repeated "so" piles up praise, and the balanced pairs, "firm, yet soft" and "strong, yet so refined", describe someone who holds opposite qualities together without strain. The rhyme of "mind" with "refined" also prepares the ground for the image that follows, because refining is what happens to metal.
That image arrives in the penultimate line: "Heaven, as its purest gold, by tortures tried." Gold is tested in fire to prove its purity, and Heaven is cast as the assayer who does the testing. The title tells us she died of cancer, but the poem never names the disease. "Tortures" is the only hint of what she endured, and the restraint matches the character being praised. The metaphor gives her suffering a meaning, as proof of purity, yet the harshness of "tortures" lets some rawness through. Judging by that word, a reader may feel a flicker of unease at a Heaven that tests its best material by burning it.
The last line is the poem's hinge: "The saint sustain'd it, but the woman died." The "but" sits in the middle, and the two halves are almost exactly balanced. "Saint" and "woman" are two names for one person. The saint is the spirit that held firm through the pain, and the woman is the body that could not. The sibilance of "saint sustain'd" sounds steady and enduring, and then "died" lands flatly at the end of the line. Because it rhymes with "tried," the trial and its outcome are locked together. Pope does not pretend that spiritual victory cancels the loss. The line holds consolation and grief together and lets neither win.
That balance is what makes the poem worth reading. An epitaph is a public form, and it invites easy flattery and stock piety. Pope's method is to refuse decoration for a woman who refused it herself. The plain diction, the negatives and the closed couplets all work as a kind of good manners. The one flash of brilliance, the gold in the fire, is saved until the very end and is then undercut by the blunt fact of death. In ten lines the poem gives a character portrait, a small argument about what we truly own, and an honest look at suffering. Few poems manage that much in so little space.