_Happiness_ is a mode of existence of which man naturally wishes the duration, or in which he is willing to continue. It is measured by its duration, by its vivacity. The greatest happiness is that which has the longest continuance: transient happiness, or that which has only a short duration, is called _Pleasure_; the more lively it is, the more fugitive, because man's senses are only susceptible of a certain quantum of motion. When pleasure exceeds this given quantity, it is changed into _anguish_, or into that painful mode of existence, of which he ardently desires the cessation: this is the reason why pleasure and pain frequently so closely approximate each other as scarcely to be discriminated. Immoderate pleasure is the forerunner of regret. It is succeeded by ennui, it is followed by weariness, it ends in disgust: transient happiness frequently converts itself into durable misfortune. According to these principles it will be seen that man, who in each moment of his duration seeks necessarily after happiness, ought, when he is reasonable, to manage, to husband, to regulate his pleasures; to refuse himself to all those of which the indulgence would be succeeded by regret; to avoid those which can convert themselves into pain; in order that he may procure for himself the most permanent felicity. Happiness cannot be the same for all the beings of the human species; the same pleasures cannot equally affect men whose conformation is different, whose modification is diverse. This no doubt, is the true reason why the greater number of moral philosophers are so little in accord upon those objects in which they have made man's happiness consist, as well as on the means by which it may be obtained. Nevertheless, in general, happiness appears to be a state, whether momentary or durable, in which man readily acquiesces, because he finds it conformable to his being. This state results from the accord, springs out of the conformity, which is found between himself and those circumstances in which he has been placed by Nature; or, if it be preferred, _happiness is the co-ordination of man, with the causes that give him impulse_. The ideas which man forms to himself of happiness depend not only on his temperament, on his individual conformation, but also upon the habits he has contracted. _Habit_ is, in man, a mode of existence--of thinking--of acting, which his organs, as well interior as exterior, contract, by the frequent reiteration of the same motion; from whence results the faculty of performing these actions with promptitude, of executing them with facility.