The citizens - that is the free men of ancient Athens - were proud of their equality, so what happened when some citizens threatened to become more equal than others?
Democracy was frequently jeopardized by the development of factions and vendettas in the Assembly. Professional politicians (called 'orators' or 'demagogues') were charismatic men who often inspired great personal loyalty. It followed that there were sometimes bitter arguments between rival supporters. If feuds were allowed to become too bitter or an unpopular politician became too strong, the business of government would be disrupted - and that would endanger Athenian democracy. So a system called 'ostracism' was invented.
Any prominent citizen who had become unpopular could be 'ostracized' by his fellow citizens - banished from the city for a period of ten years. The system worked like this: without specifying anyone's name, any citizen could propose that an ostracism be held. If the Assembly agreed to the proposal, the Agora - the market place that also acted as a civic center - was fenced off. Each of the ten tribes of Athens had its own gate through which the members would pass to vote. Each citizen voted by writing the name of the person he wished to see exiled on a fragment of pottery called an ostracon.
At least 6000 'votes' had to be cast before a citizen - the one with the highest score - could be banished. But when his ten-year exile was over, he could return and resume his life as if nothing had happened - without any dishonour or loss of rights or property.