1. If friendship is for usefulness or happiness, when this reason does not exist, it is natural that friendship will end. If you look at the wrong person, or the other person pretends to deceive, this friendship will inevitably disintegrate.

from: [Ancient Greece] Aristotle: Nicomachean Ethics

Introduction: Aristotle (384-322 BC), an ancient philosopher and ancient Greek, was one of the great philosophers, scientists and educators in the ancient history of the world, and he was a master of Greek philosophy. He is Plato's student and Alexander's teacher.

second, perfect friendship exists among good people who share the same virtues, because some virtues of these people are the same.

from: [Ancient Greece] Aristotle:

Third, friendship only exists among moral people, and they are similar to each other.

from: [Ancient Greece] Zhi Nuo: Notes on the Words and Actions of Famous Philosophers

Introduction: Zhi Nuo (circa 49- 425 BC), English Zeno of Elea, was born in Elia in the southern Italian peninsula. Ancient Greek mathematician and philosopher, famous for Zeno's paradox.

fourth, a good man is good because he is wise, and a bad man is bad because he is stupid.

from: [Ancient Greece] Plato: laris

Introduction: Plato (Plato, π λ α τ? ν, 427-347 BC), was a great philosopher in ancient Greece and one of the greatest philosophers and thinkers in the whole western culture.

five, those who make friends with benefits, if they make friends with benefits, they will make friends with each other, so that they can have real friendship. Proper friendship must be devoted to moral cultivation.

from: [Ancient Greece] Plato: Five Dialogues of Plato.