Friendship

is unnecessary, like philosophy, like art... It has no survival value; rather it is one of those things that give value to survival.
C. S. Lewis

Lewis once wrote “Friendship is born at that moment when one person says to another: “What! You, too? Thought I was the only one,” and ultimately he is right.  Friendships are built most often around common passions, common interests, and common goals.  Lewis likens the different between friends and lovers with their differing postures.  Lovers facing each other, eyes  on each other, while friends are side by side and focused on some common goal.