Unlike some European systems of the past two centuries, the American tradition is for individuals to form their own diverse communities and for each community to govern itself to the extent possible. Universal national service seems to reverse the direction of this relationship: its goal is to use the government to transform people to fit within the government's vision of what's important and how one should serve. Senator Barack Obama makes that government direction clear, promising us that his administration "will direct that service to our most pressing national challenges," eschewing the traditional American approach of having the government take its direction from the diverse choices of its people.

As de Tocqueville understood, voluntary associations are valuable not merely on account of what they accomplish, either for participants or for others, but also because they establish cultural and political forces in society independent of government. In modern society, and perhaps especially in America, each individual stands alone as an independent citizen in relation to the state, and individuals are therefore peculiarly dependent on voluntary associations to ensure that the state does not acquire a monopoly of cultural and political influence. Voluntary associations help to protect us from what de Tocqueville called "the tyranny of the majority."

In Mr. Obama's vision of voluntary organization, however, the government would develop, coordinate, and focus the efforts of private individuals and their associations, which thus would lose their independence and much of their capacity to offer alternatives to the state and its vision of life. Indeed, far from challenging the state and holding it accountable, morally or politically, many private associations would become aligned with the state. Rather than being alternatives to government, they would become its instruments.

One of John Locke's most important philosophical moves was to posit a state of limited powers. Not all good things must be within the state or be promoted by the state. For example, the sovereign could be persuaded of the good of the "one true religion" and yet could believe that it would be best for the state to be cautious about promoting that religion.

That crucial Enlightenment insight helped end centuries of European religious wars. Among twentieth-century governments, most communist, fascist, and sharia-based regimes rejected that Enlightenment view and tried to bring within their ambit all things that the state considered good -- with predictable results for human flourishing and freedom.

A key element in the rise of modern life, both its freedom and its prosperity, was the substitution of taxation for personal services, a development that allowed individuals to spend their time on what they know and love -- on tasks in which they have a comparative advantage. Being more productive as a result of this freedom, individuals can spare more of the fruits of their labor for the community.

This move from services in kind to financial payment by taxes was and is a matter of personal liberty. Such a transition was essential if individuals were no longer to be serfs in service to their lord or other communal authorities. Except for a military draft (which should be contemplated only in dire emergencies), individuals these days are mostly free to engage in voluntary activities for the benefit of themselves and others.

Mandatory community service sucks in much that is private and diverse and spits out an excessively homogenized version of the good, a version that would come with a government seal of approval.

It's probably not an accident that many American groups who tend to favor greater government largesse are relatively stingy in their own donations to charity. Nor do I think it an accident that Americans are the most generous people in the world, while the few European countries that have universal military or community service have populations that fall far short of America's in donating their time and money to the less fortunate. For charity work to be truly transformative in a positive way, perhaps it must be truly voluntary. That coerced service can be transformative without endangering freedom is even more improbable.

By bringing voluntary charitable activity under government control and by presenting his scheme as a "civilian national security force," Mr. Obama is breaking down the barriers between private and public life, between individual choice and government programs, between childhood education and adult employment, and between the diversity of freely chosen efforts on behalf of one's neighbors and subservience to the government's vision of the good.