The Greeks thrived on Agon (battle, contest, competition) first through warrior behavior, later through intellectual agon (debate) as well as with the Olympiad. Agon was aimed at achieving Aratae (perfection, excellence), making one excel at all aspects of Greek life.
The Greeks interlocked the ideas of potential and perfection. They believed that humans are born with the potential to be perfect. To be a Greek obliged one to always strive to be more successful and more perfect. This ideology is known as Paideia. Paideia required Greeks to participate in their educational, political, and competitive arenas. Paideia attempted to animate the virtues of Agon and Aratae in an attempt to shape the individual Geek's character and to preserve and promulgate Hellenic culture.
Greeks worshiped language. They saw it as a gift from the gods through Hermes. Thus, for the Greeks, language and reason were seen as one in the same. To use language was to use reason. The Greek language has the longest uninterrupted history of usage. It is also highly conducive to debate as it allows for high levels of distinction and clarity.
At this time, writing was still mechanically difficult. Therefore, most of the governance and the dissemination of paideia was done in the oral tradition. Direct speech of the citizens was the governing form of Greece. Therefore a major need for rhetorical training developed.
This new "humanistic" justice lead to the need for reasoned argument. A mental and spiritual life appeared for the first time in Greek Society. This marked the beginning of the "enlightenment." These changes also paved the way for the development of the Sophists.