[MENTION=6303]ThomasJ79[/MENTION] Also very true. The secular tradition in Western thought owe a great debt to ancient Greek thought and its later rediscovery. Its very hard to make the argument that humanist thought could have remained influential and developed and flourished much earlier.
Even in the heyday of ancient Greece religion was there. Remember Socrates was charged with corrupting the minds of the youth of Athens and of impiety ("not believing in the gods of the state"). I would argue that religion for many people in human history is essential to their being. They have an impulse, a need to believe which cannot be denied. It doesn't exist in everyone, but its there in many people and it expresses itself in different ways, though the various religions that exist on the planet. In other people this impulse is not as strong. Of course, culture also has a great deal to with how religious or irreligious people are. What makes Western culture different is the respect for the individual and also the conflict between the two points of view which continues to this day.
Consider another cultural point-of-view in Hindu culture, which instead of setting these two ideas in opposition, seeks to integrate them. In Hindu thought there are many pathways to understanding and worship/faith is not required for all of them.