The document discusses the concept of "xenia" in ancient Greece, which refers to ritualized guest-friendship between individuals from separate social groups. It was established through an exchange of goods and services meant to create a moral obligation and extend the relationship over time. Guest-friends were expected to guarantee mutual protection and help to one another, but they lived apart and had no common interests or objectives that could cause disputes. Their relationship was seen as very stable since it was not motivated by competition or disputes like relationships between fellow citizens might be. The document examines examples of guest-friendships from ancient literature and the rituals and expectations involved in the practice.