The best friend is he that, when he wishes a person's good, wishes it for that person's own sake.

Aristotle's influential treatise "Nicomachean Ethics" is considered one of the most important philosophical works ever written. In it, the ancient Greek philosopher examines what is good in life and how people should live honorably and ethically. The topic given the most time in the entire treatise is friendship, of which Aristotle saw three kinds. The lowest friendships are those of utility, in which there is no great regard for the other person beyond what they can provide. Then there are friendships of pleasure, in which two people like to be together, but the relationship is often temporary and can end easily. The highest form of friendship exists between good people who are alike in their virtuousness. In this most noble of friendships, both people truly care for each other without seeking anything in return.