Donne's earliest poems showed a developed knowledge of English society coupled with sharp criticism of its problems. His satires dealt with common Elizabethan topics, such as corruption in the legal system, mediocre poets, and pompous courtiers. His images of sickness, vomit, manure, and plague reflected his strongly satiric view of a world populated by all the fools and knaves of England. His third satire, however, deals with the problem of true religion, a matter of great importance to Donne. He argued that it was better to examine carefully one's religious convictions than blindly to follow any established tradition, for none would be saved at the Final Judgment, by claiming "A Harry, or a Martin taught [them] this."
Donne's early career was also notable for his erotic poetry, especially his elegies, in which he employed unconventional metaphors, such as a flea biting two lovers being compared to sex. In Elegy XIX: To His Mistris Going to Bed, he poetically undressed his mistress and compared the act of fondling to the exploration of America. In Elegy XVIII, he compared the gap between his lover's breasts to the Hellespont. Donne did not publish these poems, although he did allow them to circulate widely in manuscript form.
... any mans death diminishes me, because I am involved in Mankinde; And therefore never send to know for whom the bell tolls; It tolls for thee..—Donne, Meditation XVII
Some have speculated that Donne's numerous illnesses, financial strain, and the deaths of his friends all contributed to the development of a more somber and pious tone in his later poems. The change can be clearly seen in "An Anatomy of the World" (1611), a poem that Donne wrote in memory of Elizabeth Drury, daughter of his patron, Sir Robert Drury of Hawstead, Suffolk. This poem treats Elizabeth's demise with extreme gloominess, using it as a symbol for the Fall of Man and the destruction of the universe.
The poem "A Nocturnal upon S. Lucy's Day, Being the Shortest Day", concerns the poet's despair at the death of a loved one. In it Donne expresses a feeling of utter negation and hopelessness, saying that "I am every dead thing ... re-begot / Of absence, darkness, death." This famous work was probably written in 1627 when both Donne's friend Lucy, Countess of Bedford, and his daughter Lucy Donne died. Three years later, in 1630, Donne wrote his will on Saint Lucy's day (13 December), the date the poem describes as "Both the year's, and the day's deep midnight".
The increasing gloominess of Donne's tone may also be observed in the religious works that he began writing during the same period. His early belief in the value of scepticism now gave way to a firm faith in the traditional teachings of the Bible. Having converted to the Anglican Church, Donne focused his literary career on religious literature. He quickly became noted for his sermons and religious poems. The lines of these sermons and devotional works would come to influence future works of English literature, such as Ernest Hemingway's For Whom the Bell Tolls, which took its title from a passage in Meditation XVII of Devotions upon Emergent Occasions, and Thomas Merton's No Man is an Island, which took its title from the same source.
Towards the end of his life Donne wrote works that challenged death, and the fear that it inspired in many men, on the grounds of his belief that those who die are sent to Heaven to live eternally. One example of this challenge is his Holy Sonnet X, Death Be Not Proud, from which come the famous lines "Death, be not proud, though some have called thee / Mighty and dreadful, for thou art not so." Even as he lay dying during Lent in 1631, he rose from his sickbed and delivered the Death's Duel sermon, which was later described as his own funeral sermon. Death's Duel portrays life as a steady descent to suffering and death, yet sees hope in salvation and immortality through an embrace of God, Christ and the Resurrection.