Gittin 59 - For the benefit of society
Young children (6-10 years of age, depending on their intelligence) who lack a guardian are empowered to buy and sell moveable property, for the benefit of society.
In the synagogue, a Kohen is called to the Torah first, then a Levi, and after him an Israel, to foster peace and harmony. However, if there is no Kohen in the synagogue, then the Levi does not have to be called. Some even say, Levi can not be called, because people may mistakenly assume that he is a Kohen, and the Israel called after him is a Levi.