The following is a third and final excerpt from Mr. Brooks' new book, "The Road to Freedom: How to Win the Fight for Free Enterprise," which was released last week.

It seems that no matter which party is in power, the government always grows. Why is this?

The answer is relatively straightforward. Politicians get attention -- and applause -- for doing things. When things are going poorly, people never call their congressman and scream, "Don't just do something, sit there!" As a result, both Democrats and Republicans have contributed, over the decades, to the explosive expansion of the U.S. government in response to our seemingly unquenchable thirst for government services."Both Democrats and Republicans have contributed, over the decades, to the explosive expansion of the U.S. government in response to our seemingly unquenchable thirst for government services." -- Arthur Brooks

In order to reverse this trend, Americans need to lay out clear principles describing what the proper role of government is, and isn't. Advocating limited, constitutional government requires nerves of steel, a willingness to weather kneejerk resistance ("You are cutting my Medicare!"), and -- above all -- an actual philosophy. It requires a way to answer the question of what exactly needs to be limited, reformed, and cut -- and why.

So, as believers in the free enterprise system, what kind of government should we work toward? What does a limited government look like that is fair, allows people to earn their success, avoids dependency, and lifts up the downtrodden?

In his first inaugural address, Thomas Jefferson laid out his vision of "a wise and frugal Government, which shall restrain men from injuring one another, shall leave them otherwise free to regulate their own pursuits of industry and improvement, and shall not take from the mouth of labor the bread it has earned. This is the sum of good government."

President Obama's vision of government is a bit more expansive than Jefferson's. The U.S. government, in his view, should be judged on whether or not "it helps families find jobs at a decent wage, health care they can afford, a retirement that is dignified." In a bit over 200 years, we have moved from a president who believes the purpose of government is to leave you free to live your life as you see fit, to a president who thinks that the state is included in finding you a job, getting you a doctor, ensuring you save for your retirement, and a long list of other things.

We need a philosophy of government that preserves Jefferson's ethos, while recognizing that the world has changed in dramatic ways. In my view, America would do well to turn to the wisdom of German-born economist and Nobel laureate Friedrich Hayek. Hayek's classic book "The Road to Serfdom," written in 1944, is obligatory reading for all advocates of free enterprise -- and still provides an excellent guide to the role of government.

Conservatives and libertarians admire and quote Hayek incessantly. What's surprising to some is that he taught that the government, for moral as well as efficiency reasons, can and should provide a minimum basic safety net for citizens. And like most other economists, he also believed it should deal with "market failures": externalities (like crime and pollution), public goods (like the army), abusive monopolies, and information problems (such as corruption or phenomena like insider trading). But that's all -- and that is dramatically less than what the government currently does.

A philosophy of governance like Hayek's, and the courage to fight for it for as long as it takes, is what we need today. Otherwise, both parties will continue to acquiesce to every call for an expansion of government, the 2012 election will bring no real progress, and we will continue down our own road to serfdom.

Arthur C. Brooks is president of the American Enterprise Institute.