What is friendship?

What constitutes friendship? Millions of words have been devoted to the subject. Emerson said, "The glory of friendship is not the outstretched hand, nor the kindly smile, nor the joy of companionship; it is the spiritual inspiration that comes to one when he discovers that someone else believes in him and is willing to trust him with his friendship." An anonymous wordsmith decided, "A simple friend thinks the friendship over when you have an argument. A real friend knows that it's not a friendship until after you've had a fight."