By way of bringing out the advantages of friendship, it is next asked, Does the happy man need friends? To this, it is answered, (1) That happiness, being the sum of all human good, must suppose the possession of the greatest of external goods, which is friendship. (2) The happy man will require friends as recipients, of his overflow of kindness. (3) He cannot be expected either to be solitary, or to live with strangers. (4) The highest play of existence is to see the acts of another in harmony with self. (5) Sympathy supports and prolongs the glow of one's own emotions. (6) A friend confirms us in the practice of virtue. (7) The sense of existence in ourselves is enlarged by the consciousness of another's existence (IX.). The number of friends is again considered, and the same barriers stated--the impossibility of sharing among many the highest kind of affection, or of keeping up close and harmonious intimacy. The most renowned friendships are between pairs (X.). As to whether friends are most needed in adversity or in prosperity--in the one, friendship is more necessary, in the other more glorious (XI.). The essential support and manifestation of friendship is Intercourse. Whatever people's tastes are, they desire the society of others in exercising them (XII.).
Book Tenth discusses Pleasure, and lays down as the highest and perfect pleasure, the exercise of the Intellect in Philosophy.
Pleasure is deserving of consideration, from its close intimacy with the constitution of our race; on which account, in our training of youth, we steer them by pleasure and pain; and it is of the first importance that they should feel pleasure in what they ought, and displeasure in what they ought, as the groundwork (or _principium_) of good ethical dispositions. Such a topic can never be left unnoticed, especially when we look at the great difference of opinion thereupon. Some affirm pleasure to be the chief good [Eudoxus]. Others call it altogether vile and worthless [party of Speusippus]. Of these last, some perhaps really think so; but the rest are actuated by the necessity of checking men's too great proneness to it, and disparage it on that account. This policy Aristotle strongly censures, and contends for the superior efficacy of truth (I.).