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On the eve of the election, Nate Silver -- baseball forecaster, online poker whiz, political handicapper -- placed President Obama's chances of returning to office at 86.3 percent. Not 86.1 percent. Not 87.8 percent. At 86.3 percent.

Silver's prediction is not an innovation; it is a trend taken to its absurd extreme. He is doing little more than weighting and aggregating state polls and combining them with various historical assumptions to project a future outcome with exaggerated, attention-grabbing exactitude. His work is better summarized as an 86.3 percent confidence that the state polls are correct.

The statistical analysts of politics have all their bases covered. If the state polls are correct, the aggregator gets credit for his insight in trusting them. If the assumptions contained in those polls -- on the partisan composition of the electorate or the behavior of independents -- are wrong, it is the failure of pollsters, not of statisticians such as Silver. Note to recent college graduates: Strongly consider a profession in which one is right, by definition, 100 percent of the time. It beats poker.

The main problem with this approach to politics is not that it is pseudoscientific but that it is trivial. An election is not a mathematical equation; it is a nation making a decision. People are weighing the priorities of their society and the quality of their leaders. Those views, at any given moment, can be roughly measured. But spreadsheets don't add up to a political community. In a democracy, the convictions of the public ultimately depend on persuasion, which resists quantification.

Put another way: The most interesting and important thing about politics is not the measurement of opinion but the formation of opinion. Public opinion is the product -- the outcome -- of politics; it is not the substance of politics. If political punditry has any value in a democracy, it is in clarifying large policy issues and ethical debates, not in "scientific" assessments of public views.

The current mania for measurement is a pale reflection of modern political science. Crack open most political science journals and you'll find a profusion of numbers and formulas more suited to the study of physics. In my old field of speechwriting, political scientists sometimes do content analysis by counting the recurrence of certain words -- as though leadership could be decoded by totaling the number of times Franklin Roosevelt said "feah" or George W. Bush said "freedom."

This trend in social science, according to Yuval Levin of National Affairs, is "driven by a deep yearning -- fed by a kind of envy of modern natural science and its power -- for the precision of mathematics in a field of study whose subject can yield no such certainty." The modern belief that only science yields truth results in the application of scientific methods beyond their proper bounds, and the dismissal of other types of knowledge, including ethical knowledge. Political science seems particularly susceptible to precision envy.

Politics can be studied by methods informed by science. But it remains a division of the humanities. It is mainly the realm of ethics -- the study of justice, human nature, moral philosophy and the common good. Those who emphasize "objective" political facts at the expense of "subjective" values have strained out the soul and significance of politics. It is an approach, in the words of G.K. Chesterton, "that stores the sand and lets the gold go free."

Over the last decade, there has been a revolt among political scientists against a mathematical methodology that excludes substantive political debates about justice and equality. A similar revolution is increasingly needed in political commentary. The problem with the current fashion for polls and statistics is that it changes what it purports to study. Instead of making political analysis more "objective," it has driven the entire political class -- pundits, reporters, campaigns, the public -- toward an obsessive emphasis on data and technique. Quantification has also resulted in miniaturization. In politics, unlike physics, you can only measure what matters least.

And so, at the election's close, we talk of Silver's statistical model and the likely turnout in Cuyahoga County, Ohio, and relatively little about poverty, social mobility or unsustainable debt. The nearer this campaign has come to its end, the more devoid of substance it has become. This is not the advance of scientific rigor. It is a sad and sterile emptiness at the heart of a noble enterprise.

Email Michael Gerson of The Washington Post at michaelgerson@ washpost.com.