Felicity is a continual progress of the desire from one object to another, the attaining of the former being still but the way to the latter. The cause whereof is that the object of man's desire is not to enjoy once only, and for one instant of time, but to assure forever the way of his future desire. And therefore the voluntary actions and inclinations of all men tend not only to the procuring, but also to the assuring of a contented life, and differ only in the way, which ariseth partly from the diversity of passions in diverse men, and partly from the difference of the knowledge or opinion each one has of the causes which produce the effect desired.

The First Part, Chapter 11, p. 47. - Leviathan (1651)