What linked this complex tribal reform to Athenian democracy was the Council of Five Hundred, or Boule. Each tribe selected 50 council members for the 500-member Boule, usually chosen by lot. It formed an absolutely vital role in the new 'democracy' because it carried out the everyday work of the assembly and provided a permanent council that could make decisions when the assembly was not in session.

This was important because the popular assembly met on average only every nine days, and sometimes didn't meet for several weeks. It was also prone to being dominated by people living in and close to the city of Athens. In contrast, the council members of the Boule came from all over Attica and because they were duty-bound to remain in the city for a certain period of the year, they could ensure the affairs of the whole region were not neglected.

Furthermore, at least 50 of the Boule's members had to be on duty in Athens at all times. As such, they could make sure things discussed at the assembly actually got done, as well as act as a safeguard against any would-be tyrant trying to seize power.

Academics sometimes call the form of government Cleisthenes established isonomy (meaning a government of equals) because it would take until the time of Pericles before democracy really came into own.