From “Remarks on the Stoics” by Allen Thornton (link):
Suppose that you were the only person in the universe. You could exist in the most perfect paradise without reflecting on your good fortune. You could suffer hunger, thirst, and pain and not complain about the “unfairness” of existence. Notions of good and evil, just and unjust, cannot exist unless there are other people and other lives. When we judge these matters, we usually look no further than our neighbors. Americans call people poor whose standard of living would be considered quite high in China. They take for granted luxuries that were unimaginable 200 years ago. A time may come when our descendants will consider our lives horribly brutal and short, but we do not complain so long as we live about as well as those we see frequently or know about.
It would be simple to understand the Stoics’ view of reality if we didn’t have to deal with other people. But people can steal from us, make demands on us, depend on us, and interact with us in thousands of ways. The question of our relations with other people is the most complicated one in any religion or philosophy. Epictetus explains how a Stoic can maintain his serenity in the face of obviously predatory people. He cites the case of a thief who steals your clothes. “Do not admire your clothes and then you will not be angry with the thief. Do not admire the beauty of your wife, and you will not be angry with the adulterer.” He reasons that the thief “does not know wherein man’s good consists, but he thinks that it consists in having fine clothes, the very thing which you also think.” The Stoic knows that a man’s good is in his will and character and not in anything external to him.
His logic is an example of a greater truth: Inequality leads to harmony; equality leads to conflict. We are constantly told that the opposite is true, but we should consider the relations between people. Trade and commerce depend on the fact that individuals place a different value on money. If the grocer didn’t value the bag of flour less than the customer, he wouldn’t sell it. Suppose the bag were worth a dollar to the grocer and a dollar to the customer; then the grocer would have no incentive to sell it. But the grocer values the bag at less than a dollar and so both the grocer and the customer can increase their wealth by the trade of one dollar for one bag of flour. Or suppose a rich man wants to hire a person for a job and two qualified applicants apply. The applicants are not in conflict with the rich man but with each other. Or suppose a man is in love with a beautiful woman. He is in harmony with other women and with homosexuals because they do not value the woman the way he does. Their feelings toward her are completely different from his. He feels the most hatred and ill-will toward another man who also loves the woman. Conflict is in direct proportion to equality. Of course, politics turns everything on its head. Groups of similar people with similar values combine to exert pressure to achieve political ends. But even in this case, the group is simply trying to obtain something from the government at the expense of other groups who want the same thing.