We have this technology called representative democracy which allows us to make that determination. Other societies have other technology. It all boils down to might makes right in the end though.

That is how laws get made, it is not how a person decides their ideas about the roles of government. I am asking the latter.

Probably the same answer to "how do people form beliefs?"

Off the top of my head, I'd say a combination of genetics (studies show political leaning has a genetic component) and input (from social circles and reading).

It's easy for me to decide on government intervention.

I believe voluntary association is the only moral form of governance.