Classicist: In the ancient Athenian democracy, unlike in any other political system in world history, the legislature consisted of all eligible voters. Athenian voters, not elected representatives, made all political decisions by direct vote after public debate in the Assembly. Thus, if the world has ever known true democracy, it was only in ancient Athens. The conclusion of the classicist's argument follows logically if which one of the following is assumed? ['Athens was the only city in ancient Greece that had a democratic political system.', 'Most political systems in world history have not been democracies.', 'Public debate is an essential part of any democratic decision-making process.', 'A political system is not a true democracy unless the eligible voters themselves vote directly on all political decisions.']