Aristotle, a Greek philosopher who lived from 384-322 B.C., thought that friendship was an important issue to think about. As a matter of fact, he spent much of his book "Nichomachean Ethics" talking about that very thing: friendship. He believed that there are three parts to friendships, and that all three parts must be present. Two people are friends if: 1) they have good will toward each other, 2) this good will is because of the motive of either usefulness, pleasure or moral goodness, and 3) the other person knows that the other has good will toward him. A friendship based on usefulness would mean that the friends help each other do things. A friendship based on pleasure means that the people like to do activities together, and a friendship based on moral goodness is where the people help each other do the right thing.
There are some things that Aristotle didn't address though, like if freinds can be of different ages, or religions or sexes, and if people who play on the same sports team are necessarily friends even if they don't do anything with each other of the field or court. But even though Aristotle didn't think of everything, he still started people thinking about friendship in a serious way. He said that "we are a social animal by nature." So that means we are pulled to be with others--and that means friends!
Here are some quotes by Aristotle.
shows those who are not really friends."
"What is a friend? A single soul in two
"Without friends no one would choose to live,
though he had all other goods."
friend to all is a friend to none."