In The Duchess of Malfi, it's intriguing how seldom God is referenced, especially considering a cardinal, a high-ranking official in the Roman Catholic Church, is a prominent character. The characters don't turn to divine help during crises or seek absolution when they feel they've sinned. The only certainty in life is death, with no promise of an afterlife. In this play, fate governs events, not God.

Ferdinand is the most religiously conscious character, yet his version of Christianity focuses on revenge rather than love, and damnation instead of forgiveness. In Act 2, upon learning of the duchess’s child, Ferdinand's immediate reaction is to label her “a sister damn’d.” He imagines cruel punishments, expressing a wish to see the duchess and the child's father “burnt in a coal-pit” without vents so that “their curs’d smoke might not ascend to heaven.” In Act 4, he torments the duchess with horrors to drive her to despair, hoping she will renounce God and be damned upon her murder. Clearly, Ferdinand's religious beliefs are driven by madness and fury, not true religious doctrine.

Other characters look elsewhere for understanding. Antonio uses astrology to predict that his first child will have a “short life” and face a “violent death.” The cardinal, whose lavish lifestyle and mistress indicate a deviation from church teachings, does not advise the duchess to seek divine guidance if she considers remarrying. Instead, he declares, “your own discretion / Must now be your director.” When Cariola cautions the duchess against using a fake religious pilgrimage to deceive her brothers, the duchess dismisses her as “a superstitious fool.” Though the duchess kneels in her final moments to ease her passage to heaven, her last words lack true faith.

Among the characters, Bosola experiences the most profound transformation and expresses his inner thoughts most clearly. Witnessing the siblings' actions, he gains insight into the distinction between being a good servant and a good person, developing admiration for Antonio's integrity and the duchess's grace. If anyone might turn to God at the end, it would be Bosola, but he doesn't. Instead, after accidentally killing Antonio, he sums up the play's central philosophy: “We are merely the stars’ tennis-balls, struck and banded / Which way please them.”

A central theme in The Duchess of Malfi is the notion that people are unreliable and appearances can be misleading. Both virtuous characters and villains alike conceal their true intentions. In Act 1, numerous instances of deceit establish the play's foundation: the cardinal pretends not to be interested in Bosola; Bosola is employed to spy on the duchess while pretending to care for her horses; the duchess acts indifferent to marriage; and Cariola hides behind the arras without Antonio’s knowledge, promising the duchess to “conceal this secret from the world / As warily as those that trade in poison / Keep poison from their children.” Even Antonio, who is known for his honesty, agrees to keep their marriage hidden. The duchess laments that wealthy women cannot openly express their emotions and are “forc’d to express our violent passions / In riddles, and in dreams, and leave the path / Of simple virtue, which was never made / To seem the thing it is not.”

Throughout the play, deception and disguise persist. The duchess and Antonio concoct stories to conceal the birth of their first child and their plans to escape to Ancona. Ferdinand presents the duchess with a dead man’s hand, knowing she will mistake it for Antonio’s, and shows her wax figures resembling her husband and children. Bosola visits the imprisoned duchess in various disguises, including those of an old man and a bellman. Even Bosola’s single act of kindness is deceitful, as he falsely assures the dying duchess that her husband is alive and reconciled with her brothers. The cardinal kills Julia, with whom he has been having a secret affair, using a poisoned holy book, not realizing that Julia has concealed Bosola behind the door. Ultimately, the cardinal, Bosola, and Ferdinand die without help because the cardinal has lied to keep the servants from entering his chambers.

Despite these deceptions failing to achieve their intended goals, the characters consistently turn to secrecy and disguise to navigate their world, as if they know no other way. This paints a bleak picture, as Bosola realizes just before his death: “O, this gloomy world! / In what a shadow, or deep pit of darkness, / Doth womanish and fearful mankind live!” If the world is governed not by a benevolent God but by indifferent stars, and if people cannot trust their own perceptions to navigate it, it indeed presents a grim reality.