--- Voltaire, closing words of Candide (1759). In the marvellous George Washington's False Teeth: An Unconventional Guide to the Eighteenth Century (2003), Robert Darnton argues that the novel poses the question, "How can happiness be found?" Voltaire's answer, he suggests, is "Happiness lies in the cultivation of the garden."
Quote in context, in the translation by Philip Littell; available from Gutenberg.org:
The whole little society entered into this laudable design, according to
their different abilities. Their little plot of land produced plentiful
crops. Cunegonde was, indeed, very ugly, but she became an excellent
pastry cook; Paquette worked at embroidery; the old woman looked after
the linen. They were all, not excepting Friar Giroflée, of some service
or other; for he made a good joiner, and became a very honest man.
Pangloss sometimes said to Candide:
"There is a concatenation of events in this best of all possible worlds:
for if you had not been kicked out of a magnificent castle for love of
Miss Cunegonde: if you had not been put into the Inquisition: if you had
not walked over America: if you had not stabbed the Baron: if you had
not lost all your sheep from the fine country of El Dorado: you would
not be here eating preserved citrons and pistachio-nuts."
"All that is very well," answered Candide, "but let us cultivate our
garden."
