My late constitutional law professor once offered the following hypothetical about a fishing dispute that made its way to court. On one side were Native Americans; on the other, environmentalists. After a pregnant pause, he mused: "What's a liberal to do?" Were he to teach the class today, he might well have asked, "What's an empathetic judge to do?"

As this hypothetical illustrates, empathy, the factor by which President Obama claims that he selects his judicial nominees, is highly subjective, and provides little direction for judges. In some cases, all of the parties are sympathetic. In other cases, none are. In still other cases, the law may be unambiguously on the side of a party who is less sympathetic.

If empathy is the guiding principle, how is a judge to decide these cases? And how do we separate empathy from personal bias?

Here, then, is a modest proposal: In choosing nominees, President Obama should seek judges who would apply the Constitution and the laws as they are written, and interpret them consistent with their plain and original meaning.

Contrary to the frequent howls from the left, interpreting statutes and even the Constitution is not so difficult or arcane a task that judges need resort to tea leaves or to breathe subjective "life" into documents. Yes, in some cases this will lead to decisions that the judges personally consider bad policy. In these cases there is a corrective in the legislature, whose job it is--with apologies to Judge Sotomayor--to make policy.

Not only is this the correct understanding of a judge's role, it's the one that resonates best with the American people. A November 2008 nationwide survey commissioned by the Federalist Society found that 70 percent of voters want judges who "will interpret and apply the law as it is written and not take into account their own viewpoints and experiences" over judges who "will go beyond interpreting and applying the law as written and take into account their own viewpoints and experiences."

But Obama said recently that he wants judges whose personal preferences affect the outcome of their decisions. In a speech before Planned Parenthood, then-candidate Obama said: "We need somebody who's got the heart--the empathy--to recognize what it's like to be a young teenage mom. The empathy to understand what it's like to be poor or African-American or gay or disabled or old--and that's the criteria by which I'll be selecting my judges."

President Obama's nominee to the Supreme Court, Judge Sonia Sotomayor, takes this line of reasoning a step further, questioning whether it is possible for judges to overcome personal sympathies or biases "in all or even in most cases." She even seems to think that ruling based upon these biases is somehow patriotic: "I wonder whether by ignoring our differences as women or men of color we do a disservice both to the law and society."

And apparently she finds the differences between ethnicities to be profound, in a way that most reasonable people will find profoundly disturbing. She infamously claimed that she "hope[s] that a wise Latina woman with the richness of her experiences would more often than not reach a better conclusion [as a judge] than a white male who hasn't lived that life." She also stated that physiological differences based on national origins "will make a difference in our judging," and grants some credence to the idea that race or ethnicity may lead to "basic differences in logic and reasoning."

In light of these disturbing quotes, the question must be asked--and hopefully asked repeatedly by senators--will these stereotypes and identity politics inform Judge Sotomayor's "empathy?" As U.S. Civil Rights Commissioner Todd Gaziano, responding to these claims, has stated: "[T]his is not a potential example of 'reverse discrimination.' At issue is the same, old, ugly racial discrimination and stereotypes as before--just in furtherance of different groups."

Among the images of justice at the Supreme Court is Themis, the famous statue of lady justice holding a scale while wearing a blindfold. She represents the role of a judge--someone oath-bound to impartially "administer justice without respect to persons." President Obama and Judge Sotomayor's fealty to identity politics clashes with this proper role.

Senators must question Judge Sotomayor carefully to assess whether she can genuinely put aside her biases, or, as she seems to have done in the past, embrace them. The American people deserve to know whether she will serve the Constitution--or identity politics.

Robert Alt is a senior Legal fellow and deputy director of the Center for Legal and Judicial Studies at The Heritage Foundation (heritage.org).