The good life as it has been described in the earlier books of the Ethics finds its culmination in the virtue of friendship. It is here that one's activities are characterized not by mere obedience to the laws of duty but by a certain spontaneity which is the expression of one's desires and which finds fulfillment in a mutual sharing with others of the best things in life. The basis of friendship is found in the natural instinct of kinship which is present at least to some extent even in the lower animals where a kind of mutual attachment exists between parents and their offspring. On the human level it can be seen in the attraction which members of the opposite sex have for one another and in the attitude which people have toward their own relatives in contrast to their behavior toward strangers. Plato had taught that all men have a natural desire for immortality and this finds expression in doing those things that will cause them to be remembered with favor by succeeding generations.
Aristotle's high regard for friendship can be seen in the way he guards against that type of relationship which is based on selfish and ignoble motives. He is especially critical of the Epicurean types of friendship in which one's interest in the friend is the pleasure or economic gain he can get out of it for himself. This, according to Aristotle, is quite unworthy of the good man. He did not mean there is anything wrong about deriving pleasure or other advantages from one's association with others but he did insist that no true friendship could be based alone or even primarily on this type of motivation. To be sure this kind of so-called friendship based on selfish motives is quite common. Man is a social animal and he is so constituted that he enjoys association with others and as a rule he derives many advantages from it. But friendships based primarily on these considerations are likely to be of short duration. As soon as one ceases to derive these benefits to himself the friendship will be broken.
In contrast with these Epicurean types Aristotle advances a conception of friendship based on a higher motive. While pleasure and other advantages are not necessarily excluded it is not for their sake that the friendships are formed. Rather it is the worth of the individuals who are involved that constitutes the basis on which these friendships are formed and maintained. It is derived from the reciprocal recognition by two persons of this worth in each other and leads to mutual love and devotion. The personal worth of an individual consists in the development within him of the spiritual qualities of wisdom, efficiency, and refinement. It consists in the use of his natural abilities as instruments for the realization of truth, beauty and goodness. These are qualities which transcend the temporal affairs of everyday life and give to one's existence something of eternal significance. When one sees these values in another he is drawn to that person by something that has lasting value and hence the friendship will not cease when hardship or misfortune should occur. In other words the friend is an end in himself and not primarily a means for the enrichment of the other person's life.
Friendships of this type may occur under a wide variety of circumstances. When this relationship exists between husband and wife it becomes the basis of an ideal marriage. Between parents and their children where the achievements are of unequal proportion the giving and the receiving will be of different amounts and in a ratio that is directed toward equality. Friendship is also the basis for an ideal community life in which each member of the society is making a contribution toward the welfare of the group and in turn finds his own life enriched through participation in the achievements of others.