One of the most illuminating moments of the 2008 presidential race came this past Sunday. Speaking to an audience in Iowa, John Edwards said that under his proposed universal health care plan, Americans would be required to go to the doctor regularly for preventative exams:

It requires that everybody get preventive care. If you are going to be in the system, you can’t choose not to go to the doctor for twenty years. You have to go in and be checked and make sure that you are OK.

This raises some obvious practical questions: What’s the penalty for choosing not to go to the doctor? Will the government keep records of people’s doctor visits? Are you also required to comply with doctor’s advice about diet and exercise? But it also offers some political and philosophical insight into the long, bitter argument over health care.

Politically, it highlights the extent to which the Democrats have begun to make themselves vulnerable on health care by overreaching. In part because Republicans have been absent from the debate, Democrats have convinced themselves in recent years that the public wants a universal, single-payer system. Their internal debate has been about whether the government should merely fund or actually own and run that system.

This is basically nuts. Examined carefully, public concerns about health care do not amount to a rejection of America’s private health insurance system. Rather, these concerns express anxiety about access to that system, and about portability and stability of coverage. Republicans slowly are coming to champion modest reforms that address these anxieties. In time, Democrats will find that they have vastly overshot the mark with their arguments for replacing the current system with a massive bureaucracy. Calls for mandatory doctor visits won’t help them refute criticisms on that score.

But Edwards’s idea has farther-reaching, philosophical implications. The case for universal health care has long been made on the grounds that access to care should be a right enjoyed by all—we all get sick and suffer injury; no one is more entitled to help in that struggle than anyone else. This thought proceeds from an essential premise of the modern worldview: nature is out to get us, and our vulnerability defines our common humanity.

Edwards’s move points out an important weakness in that view. By turning health from a right into a duty, from protection into obligation, it elevates health to a civic virtue of the highest order—higher even than freedom. (Or, as René Descartes put it 370 years ago, health is “without doubt the primary good and the foundation of all other goods of this life.”)

This elevation of health may not bear directly on the presidential race, but it is at the heart of many modern predicaments, and helps us understand a lot about the close but often stormy relationship between liberal democracy and modern science. (Some further thoughts on that here.) John Edwards didn’t mean, I’m sure, to imply all of that. It just sits beneath his proposal, and shows how deeply the daily grind of campaign politics and the abstract realm of political philosophy are connected.