Aristotle argued that the state is the form of society with the highest purpose:
“Every state is an association of some kind, and every association is established with a view to some good; for mankind always act in order to obtain that which they think good. But, if all associations aim at some good, the state or political association, which is the highest of all, and which embraces all the rest, aims at good in a greater degree than any other, and at the highest good.” 1
But what would make the state the highest association: that it “embraces all the rest”? It does not. If two traders, one from Aristotle’s adopted city of Athens, and one from Athens’ mortal enemy Persia, contrive to evade political restrictions and trade with each other, then they are associating with each other. They have an association: one which transcends the bonds imposed by the brutish quarrels between their two states. Of course even broader associations than that existed, even in the ancient world. Let us say the Persian trader exchanged some gold for spices from an Indian trader. Then the Persian trades those spices for some pottery with the Greek trader. This is the kind of trade that happened countless times over in antiquity. And therein we have a super-national association that transcends a city-state, a kingdom, and an empire: and one which stretches from the Aegean Sea to the Indus Valley. It is the society that manifests out of peaceful world trade, and not the state, which “embraces all the rest”.
Furthermore, I would argue that a state is not even an association at all. Would you call the relation between a bandit and his victim an “association”? If not, then neither should you so term the relation between a ruling caste and its subject population.
1 Aristotle, Politics, Book 1, Part 1