In choosing a Supreme Court justice, President Obama--like any president--should look for someone who will apply the Constitution and the laws as written, and interpret them consistent with their plain and original meaning.

Regrettably, in selecting Sonia Sotomayor, Obama has rejected this criterion. Instead, he has chosen a judge who has expressed both openness to judicial policymaking and a belief that judges probably cannot be, and perhaps should not be, impartial.

Judges' proper roles are limited. Their job is not to choose the best policy or decide who they would like to win the case, but to apply the law evenly, as it is written, even if they happen to disagree with it or have greater affinity for one of the parties.

A majority of Americans agree. A November 2008 survey conducted by the polling company found 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 says he wants a judge to take personal experiences into account. He has found just such a jurist in Sotomayor.

In a speech at the University of California at Berkeley law school, Judge Sotomayor questioned whether it is possible for judges to overcome personal sympathies or biases "in all or even in most cases."

More troubling, she seems to think expressing these biases is a good thing.

"I wonder whether by ignoring our differences as women or men of color we do a disservice both to the law and society," she has said.

Also troubling, Sotomayor has made several statements which are, at best, ethnically insensitive. Best, known, perhaps, is her assertion: "I would hope 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."

U.S. Civil Rights Commissioner Todd Gaziano cuts to the heart of the matter: "Make no mistake, however: this 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."

These statements raise serious concerns about Obama's use of "empathy" as the standard for choosing judges. Empathy is an empty standard, absent direction by some guiding philosophy, ideology or personal experiences.

If judges are nominated for their willingness to make decisions based upon empathy, senators must conduct a much more searching review of nominees.

Questions about personal beliefs, politics and background are virtually irrelevant for nominees who properly limit their jurisprudence to what Chief Justice Roberts called the umpire-like task of deciding cases based on the written law. But they must be asked if a senator is to understand when and how a judge will exercise empathy to supersede the law. Given Sotomayor's public statements about the differences in judges and ethnicities, searching inquiry will be essential.

Supreme Court justices take an oath to "administer justice without respect to persons," to "do equal right to the poor and to the rich" and to "faithfully and impartially discharge" their duties under the Constitution. Judge Sotomayor has stated impartiality is not possible in most cases.

The Senate has a duty to thoroughly question Judge Sotomayor to determine whether she can honestly uphold this oath of office, or whether she will seek to apply her own personal biases from the bench.

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