Candide grows up in the Westphalian castle of Baron Thunder-ten-Tronckh, a gentle and credulous youth. His tutor Pangloss teaches that there is no effect without a cause, that this is the best of all possible worlds, and that noses were formed to bear spectacles. Caught kissing the Baron's daughter Cunegonde behind a screen, Candide is kicked out of the castle, and his education by catastrophe begins.
Recruiters press him into the Bulgarian army, where he runs the gauntlet and watches a battle whose cannons flatten six thousand men a side, a spectacle the narrator calls heroic butchery. In Holland a preacher fresh from an hour's sermon on charity refuses him bread, while James, a kindly Anabaptist, takes him in. Pangloss reappears as a beggar eaten by disease, James drowns in Lisbon harbour saving an ungrateful sailor, an earthquake kills thirty thousand people, and the Inquisition stages an auto-da-fe to prevent further tremors, hanging Pangloss and whipping Candide. Bleeding and bewildered, Candide asks what the other worlds can be like if this is the best one.
Cunegonde turns out to be alive, kept between a Jewish merchant and the Grand Inquisitor. Candide kills both men and flees with her and a practical old woman whose own history of piracy, slavery, plague, and mutilation ends in the confession that she still loved life and could never throw the burden down. In Buenos Ayres Cunegonde stays with the governor, while Candide, having stabbed her Jesuit brother for forbidding the marriage, escapes with his valet Cacambo into El Dorado, a sealed country where gold lies in the roads, lawsuits and prisons do not exist, and the sciences have a palace. They leave anyway, loaded with treasure, preferring to recover Cunegonde and to be rich among ordinary men.
The fortune drains away. Sheep sink in morasses, a Dutch skipper sails off with most of what remains, and outside Surinam a slave missing a hand and a leg explains that mutilation is the price at which Europeans eat sugar. Candide renounces optimism, defining it as the madness of maintaining that everything is right when it is wrong, and takes on Martin, a poor scholar convinced that God has abandoned the globe to some malignant being. Paris fleeces him with a sham Cunegonde and an officer bought off with diamonds, the money he gives Paquette and Friar Giroflee only deepens their misery, the Venetian senator Pococurante owns everything and enjoys nothing, and six dethroned kings share a Carnival supper with him.
The survivors gather on a small farm near Constantinople, where Candide marries a Cunegonde grown ugly and the household sours in idleness. A famous dervish refuses their metaphysics, asking whether a king who sends a ship to Egypt troubles himself about the comfort of the mice on board. An old Turk, content on twenty acres, says that his family's labour keeps off three great evils: weariness, vice, and want. Candide's verdict, that we must cultivate our garden, sets the whole company to work, and each member turns out to be of some use. When Pangloss once more chains together the causes that brought them there, Candide gives the book's last word: all that is very well, but let us cultivate our garden.