The Supreme Court this week approved Indiana's "Voter ID Law," which mandates that voters must present some form of photo identification issued by the government in order to cast a ballot when they vote at the polling place.

Such a law may seem unnecessary to those of us who vote in central Maine. Here, it seems that nearly every voter is known personally to at least one of the volunteers staffing the polls. We are generally inclined to trust that people are who they claim to be.

But we are the exception, not the rule.

In most parts of the country, voting takes place in much larger precincts, where the voters and staff are largely unknown to one another.

Indiana argued that its photo-ID requirement is nothing more than a common-sense measure designed to assure the integrity of elections, by requiring that voters demonstrate that they really are who they claim to be when they come to the polls.

Opponents of the law note that some people, particularly among the poor and elderly, do not have drivers' licenses or passports. Even though the state promises to provide a voter's ID card for free, voters seeking that ID card still will be required to supply a copy of their birth certificate or some other document confirming their identity.

And the individual voters, not the state, will have to bear the costs in time and money of gathering these documents.

What most provokes the measure's opponents, however, is that they see no need for the law because hardly any evidence exists to show that in-person voter fraud is a real problem.

The only actual case of such fraud discussed by the court took place in the New York City elections of 1868 when William M. "Boss" Tweed's political machine gained control of the city.

Thus, to the opponents, Indiana's Voter ID Law looks like a tax on voters, with no purpose other than to keep those unable to pay it from voting. And since the Supreme Court in 1966 ruled that the Fourteenth Amendment precludes the states from imposing such taxes, they conclude that Indiana's law must be invalid.

By a vote of 6-3, however, the Court rejected that line of argument.

We live in an age when one cannot board an airplane, walk into a federal building or enter almost any private, big-city office building or check in to a hotel room without showing a government-issued photo ID.

Given that context, the Court correctly held that the requirement to show photo ID at the polls does not unreasonably interfere with the right to vote. If we have to prove we are who we claim to be in order to rent a hotel room, shouldn't we also have to prove we are who we claim to be when we vote?

The New York Times' editorial, opposing the Court's ruling, hints darkly that the Voter ID Law was a Republican plot to disenfranchise Democrats. But neither of the lower courts that considered the case nor the Supreme Court could identify any individual voter who would be prevented from voting by the new requirement.

The significance of Indiana's Voter ID Law does not lie in any partisan effect it may have because it is unlikely to have any.

Its true significance lies in its recognition that our society must come to grips with the fact that most Americans no longer live in a face-to-face society, where our personal relationships with fellow citizens give us sufficient grounds to trust one another.

We can no longer take it on faith that the people who enter an office building or get on an airplane with us won't try to blow it up. We can no longer take it on faith that people who claim to be citizens or legal immigrants really are so. Nor, says the Supreme Court, must election volunteers any longer take it on faith that voters are who they say they are.

Since our personal relationships can no longer supply the grounds for social trust, the law steps in to supply those grounds by making it easier for us to verify the claims of other persons who are personally unknown to us. That is why, increasingly, we are being asked to show ID where none was needed -- and why, eventually, we will need a secure, national form of identification.

In our increasingly anonymous society, we must verify -- then trust.

Joseph R. Reisert is associate professor of American Constitutional Law and chairman of the Department of Government at Colby College in Waterville.