Candide: Or, All for the Best is a French satirical novel written by Voltaire (1694–1778), first published in 1759. In Candide, Voltaire satirizes the philosophical cult of the theory of optimism, which was popularized by German philosopher and mathematician Gottfried Wilhelm Leibniz (1646–1716).

The most notable and pervasive of the logical fallacies in Candide is the idea developed by Leibniz and espoused by Doctor Pangloss throughout the novel that "all is for the best." The logical fallacy is based on the philosophical premise (wholly unsupported by fact) that everything happens for the best, even the most horrendous and evil of occurrences, because out of all of the possible worlds in the universe, God had chosen the one in which people lived at the time as "the best of all possible worlds."

Another logical fallacy that Doctor Pangloss promotes is that of false or questionable cause-and-effect.

"It is demonstrable," said he [Pangloss], "that things cannot be otherwise than as they are; for all being created for an end, all is necessarily for the best end. Observe, that the nose has been formed to bear spectacles—thus we have spectacles. Legs are visibly designed for stockings—and we have stockings. Stones were made to be hewn, and to construct castles—therefore my lord has a magnificent castle; for the greatest baron in the province ought to be the best lodged. Pigs were made to be eaten—therefore we eat pork all the year round."

Doctor Pangloss falsely concludes that one thing (noses) necessarily caused another (spectacles), simply because the two things are associated with one another and therefore seem to form a cause-and-effect relationship.

This logical fallacy is carried to the extreme in chapter 6, "How the Portuguese made a Beautiful Auto-da-fe, to prevent any further Earthquakes."

After the earthquake had destroyed three-fourths of Lisbon, the sages of that country could think of no means more effectual to prevent utter ruin than to give the people a beautiful auto-de-fe; for it had been decided by the University of Coimbra, that the burning of a few people alive by a slow fire, and with great ceremony, is an infallible secret to hinder the earth from quaking.

The "logic" which the Lisbon sages apply to the earthquake problem is the same cause-and-effect fallacy that Doctor Pangloss applied to noses, legs, stones, and pigs.

Since the the Lisbon sages believed that the earthquake happened after disbelievers committed sins, they concluded that disbelievers should be burned to death in order to prevent them from sinning and thereby prevent the earthquake from happening again.

In this same chapter, Candide is whipped, and he watches as Doctor Pangloss is hanged.

Candide, terrified, amazed, desperate, all bloody, all palpitating, said to himself:

"If this is the best of possible worlds, what then are the others?"