Aristotle, Nicomachean Ethics
H. Rackham, Ed.

Now we stated¹ that happiness is not a certain disposition of character; since if it were it might be possessed by a man who passed the whole of his chosen life asleep, living the life of a vegetable, or by one who was plunged in the deepest misfortune. If then we reject this as unsatisfactory, and feel bound to class happiness rather as some form of activity, as has been said in the earlier part of this treatise, and if activities are of two kinds, some merely necessary means and desirable only for the sake of something else, others desirable in themselves, it is clear that happiness is to be classed among activities desirable in themselves, and not among those desirable as a means to something else; since happiness lacks nothing, and is self-sufficient.