Having left Eldorado, Candide and Cacambo begin their journey back to Europe. After several days into their long trek have passed, however, they have lost all but two of their sheep. Seeing an abused African slave stretched out on the road before them, the two question him, and learn that a very religious Christian man is his master. Hearing this, Candide admits to himself, "I'm through, I must give up [Pangloss'] optimism after all... It is a mania for saying things are well when one is in hell."
Next, Candide and Cacambo agree to split up, with Candide deciding to wait in Venice for Camabo, who agrees to return to Buenos Aires to bribe the governor to hand over Cunégonde. Unfortunately for Candide, a sly merchant steals two of his diamonds. Angry and dejected, Candide tries to get the authorities involved, but they are less than helpful or polite. Soon he resolves to himself that if there is a place where everything is for the best, "it is in Eldorado and not in the rest of the world."
Wanting a companion for his voyage, he asks a few nearby people if they wish to travel with him in exchange for lodging and money. Wanting to reward the most unlucky applicant, Candide finally selects a scholar who seems to have had a horrible lot in life.
The scholar, named Martin, who Voltaire explains is very learned in the area of identifying moral evil, and Candide, who is also quite practiced in the art, begin their journey. Despite his experience, Voltaire admits that his protagonist still subscribes to optimism, since he still has hope of one day seeing Cunégonde.
Talking philosophy with his new valet, Candide learns that Martin is a Manichee, a believer in a world with almost equal amounts of good and evil. He sums up his philosophy, saying, "In a word, I have seen so much and suffered so much, that I am a Manichee."
Outside they see two warring ships, one of which sinks. Eventually Candide learns, when a red sheep floats to the surface, that the sunken ship carried his stolen treasure. Candide tries to use this event to his advantage in his argument with Martin, asserting that the thief received his just reward. Martin, however, astutely points out that many innocent people also died when the ship went down.