As the Senate awaits the nomination of a new Supreme Court justice, a frank discussion is needed on the proper role of judges in our constitutional system. For 30 years, conservative commentators have persuaded the public that conservative judges apply the law, whereas liberal judges make up the law. According to Chief Justice John Roberts, his job is just to “call balls and strikes.” According to Justice Antonin Scalia, conservative jurists merely carry out the “original meaning” of the framers. These are appealing but wholly disingenuous descriptions of what judges — liberal or conservative — actually do.

To see why this is so, we need only look to the text of the Constitution. It defines our most fundamental rights and protections in open-ended terms: “freedom of speech,” for example, and “equal protection of the laws,” “due process of law,” “unreasonable searches and seizures,” “free exercise” of religion and “cruel and unusual punishment.” These terms are not self-defining; they did not have clear meanings even to the people who drafted them. The framers fully understood that they were leaving it to future generations to use their intelligence, judgment and experience to give concrete meaning to the expressed aspirations.

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