The proper role of government

What is the proper role of government?

We hold these truths to be self-evident: That all men are created equal; that they are endowed by their Creator with certain unalienable rights; that among these are life, liberty, and the pursuit of happiness. That to secure these rights, governments are instituted among men, deriving their just powers from the consent of the governed; that when any form of government becomes destructive of these ends, it is the right of the people to alter or to abolish it, and to institute a new government, laying its foundation on such principles, and organizing its powers in such form, as to them will seem most likely to effect their safety and happiness.

Few nations have such a clear and concise statement of the purpose and role of government as exists in the American Declaration of Independence. For over 230 years we have tried to live up to Jefferson's ideals and have so far succeeded pretty well. Jefferson himself believed that government should be limited. He had great faith in the abilities of the common people to rule themselves and was suspicious of attempts to organize a strong central government, but even he, when he assumed the presidency, had to change his mind.
During its entire history as a nation, the United States has struggled with the notion of "more vs less" government.
What do you see as the minimum amount of government necessary to achieve those ideal goals set forth in the Declaration of Independence?