As Justice Clarence Thomas approaches his 25th anniversary on the Supreme Court, it is a fitting occasion to consider his contributions to America and the Court.

More so than any other justice, Thomas has tried to recapture the Constitution's sense of the division of powers between the state and federal governments. The justice has been the most willing to reconsider whether the Court's precedents have misread the Commerce and Necessary & Proper Clauses at the expense of the principle of limited legislative powers. As he put it the Constitution does not authorize Congress to regulate "quilting bees, clothes drives and potluck suppers."

On rights, Justice Thomas seems something of a reincarnation of Justice John Marshall Harlan. He has been transfixed by equality, both the inspirational phrase from the Declaration ("all men are created equal") and the legally operative language in the 14th Amendment (no state shall deny "equal protection of the laws"). His reading of the Constitution has led him to oppose race-conscious legislation that seeks to distribute employment, contracts, and legislative seats on the basis of quotas. In the case of the First Amendment, he has shown a keen interest in protecting its core of political speech.

The justice's opinions (at this point he has authored over 500) are notable for their clarity and tightness. When he writes for the majority, his opinions supply useful guidance to lower courts and litigants. He also has crafted numerous opinions in specialized areas of law, such as securities law. Experts in these areas are often struck by his knowledge of their fields.

Although some wish to caricature Thomas as an ideologue, veteran court watchers know that he applies a consistent approach across cases. While he long ago voted to overturn Roe v. Wade, in a subsequent case he questioned whether Congress had legislative power to enact a nationwide ban on particular abortions. Even though he is often seen as tough on criminal defendants, he has sided with them when his methodological approach dictates as much. This fidelity to law inspires many.

His steadfast approach is of a piece with his general opposition to judicial discretion. The justice has argued that "[t]he greater the amount of judicial discretion, the greater the freedom to write one's personal preferences into the law. Narrow judicial discretion, and you reduce the temptation for judges to ignore their duty to be impartial." He also has been part of a welcome process in which the courts are paying far more attention to text in lieu of searching for often indeterminate statutory purposes. Justice Thomas understands that federal judges should not serve as America's Platonic Guardians, revising constitutions and statutes in the guise of interpreting them.

Having had the privilege of clerking for Thomas over 20 years ago, I can testify that his character remains unchanged. To my mind, he is the most approachable justice, each year spending hundreds of hours with school kids, law students and members of the public. He seems to know everyone at the Court, from the guards, to the cleaning staff, to the law clerks who come and go. He is ever respectful of the institution and its place in American society, even as he seeks to reshape some of its doctrines. He understands that when the Court sticks to its errors, hiding behind the doctrine of precedent, all of us are stuck with them.

The justice's position does not invariably prevail. That is an understatement. But prevail or not, the justice speaks his mind, marches to his own beat, and stays true to his duties, as he understands them. In so doing, he serves as a model for the millions of Americans, lawyers and laymen, who believe that modern constitutional doctrine has become unmoored from the Constitution's text and its origins. In Thomas, they perceive a lone wolf, untamed by Washington.

Somewhat paradoxically, this stance has won over those who tend to see things differently. Though Supreme Court observer Tom Goldstein disagrees with Justice Thomas on many questions, if "the measure of a justice's greatness is his contribution to new and thoughtful perspectives that enlarge the debate, then Justice Thomas is now our greatest justice." More and more are coming to agree.

Mr. Prakash, a former law clerk for Justice Thomas, is the James Monroe Distinguished Professor of Law at the University of Virginia. Thinking of submitting an op-ed to the Washington Examiner? Be sure to read our guidelines on submissions.