The right to the “pursuit of happiness” … tends to fuse liberty and property. It means something like this: the right to use one’s own faculties for one’s own ends or purposes. Happiness, it should be noted, did not then refer to some sort of subjective state of bliss, as we might nowadays suppose. It meant rather that satisfaction that arises from developing one’s abilities and receiving the rewards from doing so.
Clarence B. Carson, in reference to the Declaration of Independence, in A Basic History of the United States, Vol. 2: The Beginning of the Republic 1775-1825, pg.25