No state has ever been founded without religion serving as its base.
Gist of Idea
Every society has a religion as its base
Jean-Jacques Rousseau (The Social Contract (tr Cress) , IV.8)
It is not clear to me that the ancient Greek cities had religion as a 'base', though they all had a religion, and expected conformity. Religion doesn't figure much in Thucydides. Communist Russia was the first explicitly atheist state, I think.
Rousseau,Jean-Jacques: 'The Basic Political Writings', ed/tr. Cress,Donald A. [Hackett 1987], p.223