«Happiness signifies a gratified state of all the faculties. The gratification of a faculty is produced by its exercises. To be agreeable that exercise must be proportionate to the power of the faculty: if it is insufficient discontent arises, and its excess produces weariness. Hence, to have complete felicity is to have all the faculties exerted in the ratio of the several developments; and na ideal arrangement of circumstances calculated to secure this constitutes the standard of “greatest happiness”. But the minds of no two individuals contain the same combination of elements. There is in each a different balance of desires. Therefore the conditions adapted for the highest enjoyment of one, would not perfectly compass the same end for any other. And, consequently, the notion of happiness must vary with the disposition and character; that is, must vary indefinitely.» – Herbert Spencer, in Social Statics.