The base for any organized society and civilization are rules. The base for all rules is a constitution, which states the least common denominator for the organization of the group.
The constitution in a democracy is the most essential common agreement between all citizens, ideally owned, concieved/created, direct democratically ratified by the people.
Here is the „reduced to the max“ version of such a constitution and an esplanation, why we don’t need more, than two priciples: Freedom & Equality: