not the greatest possible happiness for the actor himself, but the greatest possible happiness for all who are affected by the results of the action. Stuart Mill bases this principle, not on the self-interest of the actor properly understood as Bentham had done, but on the psychological nature of the moral sentiment (Utilitarianism, 1863). In his theory of this sentiment he adopted the doctrine of the metamorphoses of sentiments as developed by Hartley and James Mill. The origin of the moral sentiment is due to the coöperation of a large number of elements: sympathy, fear, reverence, experiences of the effects of actions, self-esteem and the desire for the esteem of others. It is in this complex nature that the cause of the mystical character attaching to the idea of moral obligation is to be found. The complex may however become so completely subjective and perfect that the sentiment itself will appear as unitary. Its development ordinarily takes place under the influence of social life by which individuals are accustomed to regard common interests and to enlist united efforts. In this way a sentiment of solidarity and unity evolves which may even (as in the case of Comte's religion of humanity) assume a religious character.
But Mill not only modified utilitarianism by the emphasis which he placed on the subjective factor, but likewise by the assumption of the qualitative differences of the sentiments. He thinks "happiness" must not be estimated according to quantity alone, but likewise according to quality. He says, like Plato (in the ninth book of the Republic), that he alone who knows the various qualities of happiness from personal experience is in position to furnish a valid estimate of their different values. A Socrates dissatisfied is better than a satisfied idiot.
