The most important elements in one's friendship for others and the characteristics which distinguish the various forms of friendship in which he engages, are derived from the feelings with which one regards himself. There are five definitions of a friend:
- One who desires and performs the good, or what appears to him as the good, of another person for the sake of that person.
- One who desires the existence and life of another person for that person's sake.
- One who spends all his time in the company of another person.
- One who shares the same ideals and desires as another person.
- One who shares all the joys and sorrows of another person.
These same feelings all appear in the attitude that a good man has toward himself.
- A good man desires and does what is good for himself.
- He desires his own life and safety.
- He spends his time with himself and is happy while doing so.
- He remains consistent in his judgment, for there is no conflict between his mind and the rest of his nature, and he desires the same objects with all parts of his soul.
- He has a complete and undivided consciousness of his own pleasures and sorrows.
The two most essential characteristics of friendship are fairness and sympathetic interest, the very same features that are typical of a good man's relation with himself. A good man wishes and does what is best for the intellectual element in him (that which is most truly himself) without ever ignoring his material and irrational elements, and he is in harmony with himself at any given moment. It is not difficult to think of a good man as feeling friendship for himself if we conceive of him as a dual or composite being, and recognize that the statement, "feeling friendship for himself," is meant as an analogy or metaphor. In this sense we may say that a man can have good relations with others only when he is reasonably happy and well balanced, that his friend becomes to him like another self, and that devoted attachment to someone else comes to resemble love for himself in its intensity and unselfishness.
To some extent most people share the attributes of good men as outlined above, and this is what enables them to engage in friendly relations with other people. Studies of the behavior of criminals and other degraded types support this view by showing that bad people are unable to form permanent relationships with others and seem to manifest self-hatred in many of their acts.