My definition of the role of government is: "government exists to do the will of the majority without infringing on the rights of the minority." By "rights" I mean basically those rights outlined in most modern constitutions and bills of rights: Rights 1 through 22 of the Universal Declaration of Human Rights. If the majority wants "big government" with high taxation then I believe that governments may do so.
I reject some other "popular" definitions of the role of government. The definitions I reject have at their heart a kind of absolutism.
Anarcho-capitalism is a form of utopianism like communism or militant environmentalism. Anarcho-capitalists hold that if we got rid of the government we could "buy" protection from security firms and achieve a more or less just society without "big brother" government on our backs. It doesn't take a rocket science to see that anarcho-capitalism without any government oversight would devolve into feudalism.
Anarcho-capitalism is a form of absolutism because it declares that any centralized leadership (no matter how modest) is evil.
In general, libertarians want to maximize the power of individuals and minimize the power of the state. Most libertarians would put up with a small state that prevents citizens from shooting each other. In other words it is just to the left of anarcho-capitalism and far right of anything remotely sane.
Libertarians tend to support crazy stuff like debtor's prison, child labor and an end to all environmental protections.
In general I am against any political movement so libertine that it would not allow the state to step in and prevent the endangerment of chidren. As is discussed in this excellent satire, Libertarians can never admit to any circumstances in which government is helpful. This seems to constantly degenerate into a form of brain damage that may well be incurable. The only upside is that most average people can immediately see the holes in libertarianism much more quickly than they do communism. After all, most people (for all of their griping) like many government services such as public transportation, fireworks on holidays and racially integrated public schooling.
I believe that the state can and should use its taxation power as a force for positive change (where positive is defined by the ruled masses). Tax incentives and penalties are typically better than blanket regulations because they allow the market to find economically efficient solutions to problems.
Socialism is a system that depends on a planned economy owned by and for the workers. Some people are still trying to perfect the system!
Socialism has been tried various times. It will always devolve into dictatorship because the only way to ensure that money does not accumulate in an individual's hands is to erect a police state that monitors all transactions. It amazes me that there are still people who believe in socialism and communism. I can only conclude that they wish to believe that people could and would just share and share alike and that cheaters in such a system would be a minority. My sense of human nature suggests otherwise. Even when taxes are low there are many people who cheat the system. If taxes are 100%, the black market will tend to overwhelm -- except for that police state.