Do Republican-appointed Supreme Court justices get more liberal as they age? A formidable body of academic research suggests that they do. This idea offers a sliver of comfort to those alarmed by Donald Trump’s appointment of Neil Gorsuch and Brett Kavanaugh to the nation’s most powerful judicial body, as well as by the even more disturbing prospect that if Trump is reelected, he may get to place additional conservatives on the court.

Although no one is sure what causes this liberalizing dynamic, it’s easy to track the process in the careers of such GOP appointees as the late Harry Blackmun, the author of the majority opinion in Roe v. Wade, and, more recently, in the records compiled by retired Justices David Souter, John Paul Stevens and Anthony Kennedy. As I have pointed out in this column before, we can even discern a modest move to the left by Chief Justice John Roberts.

As with most rules and research, however, there are exceptions. Enter Justice Clarence Thomas. Unlike some of his GOP counterparts, Thomas has demonstrated no migration to the ideological center. If anything, he’s become increasingly radical over time.

Thomas, who will turn 71 in June, was appointed by President George H.W. Bush in 1991 to replace the liberal stalwart Thurgood Marshall. Marshall was the first African-American to serve on the court. Thomas is the second.

In popular culture, Thomas is still best known for his rancorous confirmation hearing, which was famously marred by accusations of sexual harassment lodged by law professor Anita Hill.

To constitutional scholars, Thomas is best known as an inflexible right-wing “originalist.” In its current iteration, originalism asserts that the Constitution should be read according to the meaning it had for the Founding Fathers rather than as a “living” document that should be interpreted not only in light of its text but also in light of contemporary values and evolving traditions.

Since arriving at the court, according to several empirical studies, Thomas has ranked as the panel’s most conservative member. Time and again, he has deployed his originalist philosophy to produce downright reactionary opinions. He issues his opinions often in dissent or as idiosyncratic concurrences, geared toward upsetting liberal precedents, returning American law to the libertarian free-market jurisprudence of the Gilded Age, and neutralizing litigation as an instrument of progressive social and economic reform.

Once confirmed, Thomas methodically unveiled his extremist outlook. In U.S. v. Lopez (1995), for example, he authored a concurring opinion encouraging his colleagues to return to the “original understanding” of the commerce clause. If that view were adopted, it could lead to the invalidation of nearly all federal labor laws.

In 1997, in Printz v. United States, in which the court overturned parts of the Brady Handgun Violence Prevention Act, Thomas argued in another solo concurrence that the Second Amendment guaranteed an individual right to own and bear arms. Eleven years later, in District of Columbia v. Heller, a 5-4 court majority embraced his analysis.

Over the years, Thomas has also staked out starkly retrograde positions on the death penalty, affirmative action, abortion, voting rights, campaign finance, gay marriage, environmental protection, religious freedom and the exclusionary rule (the principle that precludes illegally seized evidence from being introduced into evidence in criminal trials). As Thomas contended in a 2005 dissenting opinion (Gonzales v. Raich), the states, rather than the federal government or the Supreme Court, “should decide for themselves how to safeguard the health and welfare of their citizens.”

During this term, Thomas has doubled down on his efforts to turn back the judicial clock, advocating that longstanding and revered liberal precedents on freedom of the press and the right to counsel be reversed.

In Garza v. Idaho, dealing with the effective assistance of counsel in criminal cases, Thomas wrote a dissent insisting that Gideon v. Wainwright was wrongly decided. One of the pillars of modern American criminal procedure, Gideon recognized the Sixth Amendment right to court-appointed counsel at public expense for all criminal defendants facing possible prison sentences.

According to Thomas, the Sixth Amendment “as originally understood and ratified meant only that a defendant had a right to employ counsel, or to use volunteered services of counsel.”

In McKee v. Cosby, a defamation case filed by one of the many women who have accused comedian Bill Cosby of rape, Thomas maintained that the court’s unanimous 1964 landmark ruling in New York Times v. Sullivan should be overruled.

Prior to Sullivan, defamation lawsuits were governed exclusively by state law, and they were often slanted in favor of plaintiffs—especially rich ones who could afford expensive legal fees. Sullivan changed all that by establishing constitutional standards applicable throughout the country in defamation cases brought by public officials.

The justices wrote that in order to protect our “profound national commitment” to uninhibited, robust and wide-open debate that “may well include vehement, caustic and sometimes unpleasantly sharp attacks,” the First and 14th amendments must shield persons and publications sued for defamation. Public officials, they instructed, should not recover damages for allegedly defamatory statements related to official conduct unless they prove that such statements are made with “actual malice”—that is, that they are made with the knowledge that they are false or with reckless disregard for the truth.

In a series of subsequent decisions in the late ’60s and early ’70s, the court extended the actual malice standard to defamation lawsuits brought by “public figures” and celebrities.

In his opinion in the McKee case, Thomas wrote that Sullivan ran afoul of the original meaning of the First Amendment, terming it a policy decision “masquerading as constitutional law.” Coincidentally or not, Thomas’ dissent echoed the calls made by Trump during the last presidential campaign to “open up” the nation’s libel laws.

While there can be no doubt as to where Thomas stands on the ideological spectrum of the current court, commentators remain divided on the actual influence he wields on the bench and in wider conservative legal circles. As Ian Millhiser noted in a July 2018 column published by the website ThinkProgress, some observers continue to see Thomas as an intellectual lightweight or a clone of fellow-originalist Antonin Scalia, who died in February 2016. Critics have also maligned Thomas’ habit of remaining silent during the court’s oral arguments.

Millhiser, by contrast, sees Thomas as a trendsetter and a model for younger generations of conservative law students, lawyers, law professors and judges. That’s what makes Thomas, in Millhiser’s estimation, “the most important legal thinker in America.”

With Gorsuch and Kavanaugh, a new crop of conservatives has arrived at the court. If they and any other future Trump appointees follow in Thomas’ footsteps as unrelenting, inflexible originalists, we may have to throw out all the research about justices mellowing over time. In that event, Thomas won’t just go down as the most important legal thinker of the early 21st century. He’ll go down as the most dangerous.