Discourses, On Friendship — In Plain English

Epictetus — The Slave

Don't judge people by what everyone else looks at — whether they share the same parents, grew up together, or had the same teacher. Judge them by this alone: where do they place their focus? Do they care about external things or about their own choices? If they focus on externals, don't call them friends. Don't call them trustworthy, steady, brave, or free. If you have any sense, don't even call them human. The thing that makes people attack each other, abuse each other, fight over empty or public spaces like wild animals, and act like criminals in court — that's not human nature. Neither is the thing that makes them lose control, commit adultery, and corrupt others. All the harm people do to each other comes from one mistake: they place themselves and their interests in things that are not within their control.

Epictetus — The Slave Original

But examine, not what other men examine, if they are born of the same parents and brought up together, and under the same pedagogue; but examine this only, wherein they place their interest, whether in externals or in the will. If in externals, do not name them friends, no more than name them trustworthy or constant, or brave or free; do not name them even men, if you have any judgment. For that is not a principle of human nature which makes them bite one another, and abuse one another, and occupy deserted places or public places, as if they were mountains, and in the courts of justice display the acts of robbers; nor yet that which makes them intemperate and adulterers and corrupters, nor that which makes them do whatever else men do against one another through this one opinion only, that of placing themselves and their interests in the things which are not within the power of their will.