Which feature of a state believes in sharing similar beliefs in order to establish a more stable government

Population.

Explanation:

The population, as the name implies, relates to the number of people in a state. The population affects the demography of a country. It is the "bedrock" of every state.

This feature of a state feels that the people (population) must politically and socially agree to have a state with good governance. Other features of a state are;

Sovereignty Territory Government

Without the population, these other features of a state will not exist.