Let us, however, resume our discussion from the beginning. Since all knowledge and every pursuit aims at some good, what is it that we say political science aims at, and what is the ultimate end of all human action? With regard to its name, there is almost complete agreement; for both the multitude and the refined call it happiness, and they suppose that living well and doing well are the same as being happy. But as to what happiness is, they disagree, and the account given by the multitude is not like that of the wise. For some think it is one of the things that are plain and obvious, such as pleasure, wealth, or honour; others think it is something else; and often the same person changes his opinion: when he is ill, he thinks it is health; when he is poor, he thinks it is wealth. And being conscious of their own ignorance, they admire those who speak of some great thing that is beyond them. But some think that, besides these many goods, there is another good which is good in itself and which is the cause of all these goods being goods. Now, to examine all the opinions that have been held about happiness would perhaps be rather a waste of time; it is enough to examine those that are most prevalent or that seem to have some reason in their favour. And we must not forget the difference between arguments from principles and arguments to principles. For Plato, too, was right in raising this question, and used to ask whether the argument proceeded from or to the first principles, just as in a race-course the runners may start from the judges' stand and turn at the turning-point. For we must begin with things that are known; but they are known in two ways: some are known to us, others are known absolutely. Perhaps, then, we must begin with things that are known to us. That is why those who are to be properly instructed in what is noble and just, and in political science generally, must have been trained in their habits. For the starting-point is the fact, and if this is sufficiently clear to us, we shall not need to know the reason why. And such a man, or at least one who is well trained, can either himself find the starting-point or can easily learn it from another. But he who is neither one nor the other may listen to Hesiod: "He is best who knows all things himself; good, too, is he who hearkens to a wise man's voice; but he who is neither wise nor hearkens to the wise is a useless man." Let us, then, resume our discussion from the point where we digressed. The good, it seems, is something final and self-sufficient, and the final good is thought to be happiness. For we choose happiness for its own sake, never for the sake of something else; whereas honour, pleasure, reason, and every virtue we choose indeed for themselves (for if nothing resulted from them we should still choose each of them), but we choose them also for the sake of happiness, thinking that through them we shall be happy. But no one chooses happiness for the sake of these things, nor, in general, for anything else. The same conclusion seems to follow from the consideration of self-sufficiency. For the final good is thought to be self-sufficient. Now by self-sufficient we mean not what is sufficient for a man alone, who lives a solitary life, but what is sufficient for parents, children, wife, and in general for friends and fellow-citizens, since man is by nature a social animal. But we must impose some limit on this; for if we extend the requirement to ancestors and descendants and friends' friends, it would go on indefinitely. But we must consider this later. The self-sufficient we define as that which, taken by itself, makes life desirable and lacking in nothing. And happiness we think is such a thing, and indeed the most desirable of all things, not counted as one good among many. For if it were counted as one among many, it would obviously be more desirable if even the smallest of the other goods were added; for the addition would produce a greater amount of goods, and the greater amount of goods is always more desirable than the smaller. But happiness is something final and self-sufficient, and is the end of all actions. Perhaps, however, it seems that to say that happiness is the supreme good is a mere platitude, and a clearer account of it is still required. This might perhaps be given if we could first ascertain the function of man. For just as for a flute-player, a sculptor, or any artist, and in general for all things that have a function or activity, the good is thought to reside in the function, so it would seem to be for man, if he has a function. Have the carpenter and the tanner certain functions or activities, and has man none? Is he born without a function? Or as the eye, the hand, the foot, and in general each of the parts evidently has a function, may we not lay it down that man similarly has a function over and above these particular functions? What, then, can this function be? For life is common even to plants, but we are looking for something peculiar to man. We must exclude, therefore, the life of nutrition and growth. Next there is a life of sense-perception, but this is common to horses, oxen, and every animal. There remains, then, an active life of the rational part of man. Of this, one part is rational in the sense of obeying reason, the other is rational in the sense of possessing reason and exercising thought. And as this life is also spoken of in two ways, we must take the life that is active in the sense of exercising the rational faculty; for this seems to be the more proper sense of the term. Now, if the function of man is an activity of the soul in accordance with reason, or not without reason, and if we say that the function of a good man is to do this well and nobly, and if the function of anything is performed well when it is performed in accordance with its proper excellence, it follows that the good of man is an activity of the soul in accordance with virtue, and if there are several virtues, in accordance with the best and most perfect. And we must add this: in a complete life. For one swallow does not make a summer, nor does one day; and so too one day, or a short time, does not make a man blessed and happy.