Every art and every inquiry, and similarly every action and choice, seems to aim at some good; hence the good has rightly been defined as that at which all things aim. But there is a difference among ends: some are activities, others are products apart from the activities themselves. Where ends of the latter sort exist, the products are by nature better than the activities. Now, as there are many actions, arts, and sciences, the ends are also many: the end of medicine is health, that of shipbuilding a ship, that of military strategy victory, that of household management wealth. But where the ends fall under a single one—as bridle-making falls under horsemanship, and this in turn under military strategy—the end of the master art is the end for the sake of which all the others are pursued. In such cases we must not content ourselves with knowing the immediate end: it is this that commands, and the science of that superior end must prevail over the subordinate sciences. Now the science that commands, and which we ought to study, is manifestly political science, for it determines which sciences are necessary in cities, which sciences citizens should learn, and to what degree. We see, indeed, that even the most honored capacities, such as strategy, household management, and rhetoric, are subordinate to it. Since political science uses the other sciences as means, and since it legislates as to what we are to do and from what we are to abstain, its end will include the ends of all the others, so that this end will be the human good. For even if the end were the same for an individual and for a city, that of the city would appear greater and more perfect both to attain and to preserve: for while it is noble to satisfy a single man, it is nobler and more divine to satisfy a people and a number of cities. Such, then, is the aim of our inquiry, which is a kind of political science. Let us return to our starting point: what is the highest of all goods achievable by action? Verbally there is very general agreement: for both the multitude and persons of refinement say that it is happiness, and identify living well and doing well with being happy. But with regard to what happiness is, they differ, and the multitude do not give the same account as the wise. Some place it in something manifest and evident, like pleasure, wealth, or honor; some in one thing, some in another; often the same man changes his mind: when he falls ill, he thinks happiness is health; when he is poor, that it is wealth. Yet perhaps it would be better to grasp the universal good through a different path. Every art and every capacity, indeed, judges well and performs well what constitutes its own excellence; we should therefore consider what is the excellence of man. Take an example from more accessible matters: a flute-player, a sculptor, any artist—in short, all who have a definite activity and function—have, we think, a proper fulfillment consisting in the excellence of their activity. So it must be with man, if there is some activity proper to him. But is it likely that the eye has a function, and that the hand, the foot, and each member of the body in general have one as well, while man as a whole has none? That would be quite absurd. What, then, do we take to be the proper function of man? Mere life is shared with plants; but we seek what is proper to man, and we must therefore set aside the life of nutrition and growth. Next would come the sensitive life; but this too is common to the horse, the ox, and all animals. There remains the life of a being that acts according to reason: this rational activity has an element that obeys reason, and another that possesses reason and thinks. Since the rational life is expressed in an activity and not in a mere disposition, it is realized in activity in accordance with reason. We posit, then, that the proper function of man is an activity of the soul in accordance with reason, or not without reason. Now the function of any being is performed well when it is performed in accordance with its virtue, its proper excellence: thus the harpist plays well when he plays according to the excellence of his art. It follows that the good of man consists in an activity of the soul in accordance with excellence, and if there are several excellences, in accordance with the best and most perfect among them. Moreover, it must be in a complete life: for one swallow does not make a spring, nor does one day; and so neither does one day, nor a short time, make a man blessed and happy. Such, in outline, is the conception of the highest good: happiness is an activity of the soul in accordance with virtue, and if there are several virtues, in accordance with the best and most complete of them, in a complete human life.