When there is a prize for hitting a bull's-eye, one makes people want to hit the bull's-eye by showing them this prize. Still they cannot win the prize if they do not see the bull's-eye. And those who see the bull's-eye cannot be induced to aim for it if they do not know that there is a prize to win. Similarly, virtue, which is the bull's-eye, does not come to be strongly desired when it is seen on is own; contentment, which is the prize, cannot be acquired unless it is pursued.
Rene Descartes, to Elisabeth of Bohemia (18 August 1645), from The Correspondence Between Princess Elisabeth of Bohemia and René Descartes, Shapiro, ed. & tr. (U Chicago P: 2007) p. 104. This is in the midst of a discussion of Stoicism and Epicureanism, and, more precisely, in the midst of Descartes's discussion of what he agrees with in Epicurus -- he thinks Epicurus was right to say that happiness consists in pleasure in general, but thinks that critics of Epicurus are right to the extent that Epicurus was not really teaching virtue. The difference between sovereign good and true happiness is an important one for Descartes's ethical discussions in the correspondence. Virtue is our good, happiness our contentment or satisfaction of mind on having virtue; and both are the aim of life.