Donne begins the sonnet as a lawyer and ends it as a petitioner, and the poem's interest lies in the swerve between the two. The speaker opens by building a case. Poisonous minerals, the tree whose fruit "threw death on else immortal us," lecherous goats and envious serpents: none of these can be damned. So why should he be? The question is held back for three lines, and the opening is one long chain of "if… if… if" that piles up evidence before the verdict is demanded. Even here a small "alas" slips in, so a little grief seeps into the logic.
The argument then sharpens. What sets the speaker apart from goats and serpents is "intent or reason," and he complains that these faculties make "sins, else equal, in me more heinous." The same act weighs more because he understands it, so the gift of reason becomes a liability. His third move is the cheekiest. Mercy, he points out, is "easy, and glorious / To God," so it costs God nothing and earns him credit. Why then does he threaten wrath? The speaker is half-arguing, half-bargaining, and he is clever about it.
The form supports this controlled performance. The sonnet is written in steady iambic pentameter, and its rhymes follow the Petrarchan pattern: an octave rhymed *abba abba* and a sestet rhymed *cddcee*. The octave's rhymes on *us, envious, heinous, glorious* make the same "-ous" sound come round four times. It has the insistence of a complaint repeated, and the hissing sounds may remind us of the serpent. The three "why should" questions give the octave a prosecutor's rhythm.
At line 9 the argument breaks off. In line 8 the speaker talks *about* God ("his stern wrath, why threatens he?"), as if God were a defendant in the room. Then he catches himself: "But who am I, that dare dispute with thee / O God?" The shift from "he" to "thee" is small but telling, because the speaker has been talking over God's head and now turns to face him. The next line stumbles into "Oh!", and the tone cracks from debate into appeal.
The imagery of the sestet is as bold as the logic of the octave was. The speaker asks for "thine only worthy blood, / And my tears" to make "a heavenly Lethean flood." Lethe belongs to classical myth, where it is the river of forgetfulness in the underworld, and Donne brings it into a Christian prayer and calls it "heavenly." The blood is "only worthy" while the speaker's tears are merely added with an "and," a modest human contribution. The verb "drown" is violent, and what is to be drowned is "my sin's black memory." The sin that troubles him is no longer the deed but the memory of it, the dark stain that lingers.
The closing couplet turns the whole poem. "That thou remember them, some claim as debt, / I think it mercy, if thou wilt forget." Debt is the language of ledgers and courtrooms, in which justice requires that every wrong be kept on record. The speaker quietly reverses this: for him, forgetting is the real mercy. There is a paradox in asking an all-knowing God to forget, and it reads as a request that God will not hold the sins against him. The couplet's neat rhyme snaps shut like an epigram, yet the final word, "forget," leaves the wish hanging, and "if thou wilt" admits it is a hope, not a certainty.
The poem is significant for what it lets into a religious sonnet. The complaint about fairness is never refuted, and nobody answers the questions about goats, serpents and reason. The speaker simply stops arguing and starts asking. Donne makes the sonnet's structure enact a change of heart, with the octave as the mind's protest and the sestet as the heart's surrender. The poem lets doubt, cleverness and humility stand side by side, and that honesty is why a short argument about damnation still feels human.