In an essay that appeared in Friday’s Wall Street Journal, Supreme Court Justice Samuel Alito described his judicial philosophy, originalism, as the belief that “constitutional provisions should be understood to mean what the public would have taken them to mean when they were adopted.”

So originalism is more than just figuring out what the Framers meant when they wrote it, and what the great legal minds of the day would’ve interpreted it to mean. Instead, it’s what the Framers meant and what average Americans would’ve understood them to mean.

The word “public,” then, is crucial, because Alito is saying that the Constitution was meant to be a document for the American people, for average folks sitting around and discussing the issues of the day.

“It’s not the secret intent of James Madison or anyone else who had a prominent role in framing the Constitution,” Alito told Fox News’s Mark Levin last night in a 40-minute interview. “It’s what people at the time would have understood it to mean.”

In his new book, So Ordered: An Originalist’s View of the Constitution, the Court, and Our Country, which hits the shelves on Tuesday, Alito paints a picture of “ordinary voters, sitting around the fireplace in a tavern ... reading a newspaper, seeing the text of the Bill of Rights there.” These might be leading citizens, or they might be humble farmers.

“They read that it protects freedom of speech,” he continues. “It protects free exercise of religion. It says that a person may not be deprived of life, liberty, or property without due process of law. What would they have understood it to mean? These are ordinary voters.”

The so-called living constitutionalists, of course, never liked originalism because it continually thwarts them. It keeps them from making mischief by reinterpreting the Constitution for their own ends. Alito said as much last night to Levin: “Some people don’t like [originalism]. They want the Constitution to mean whatever they want it to mean at a particular point in time. They want it to protect things that it doesn’t protect. They want it to allow things that it doesn’t allow.”

Most of us already intuitively understood the simplicity and elegance of originalism, and it’s what we conservatives have come to love about Alito and his colleague, Clarence Thomas, and their former colleague, Antonin Scalia. But Alito last night offered a slightly different and equally compelling rationale for originalism, calling it “a fancy term for reading the Constitution the way we customarily read all other legal documents and in fact many other documents.”

Indeed, why should we treat the Constitution, which is after all a legal document, any differently than we treat all other legal documents?

Alito says he considers himself, more specifically, a “working judicial originalist” — a judge who tries to “achieve originalist aims within the framework of our judicial system.”

Alito believes that originalism can continue to take stronger root, or it can fail, depending on whether future judges stay on course. “I envision an originalist judge driving down a highway,” he says. “Along the way, he sees seven off-ramps. Six of these are wrong turns, and the seventh places an originalist judge at a crucial crossroads.”

Alito then goes on to describe these off-ramps, such as insecure originalism, which is practiced by judges who fail to follow the law wherever it leads and instead get caught “subconsciously setting a higher bar for legal arguments that yield outcomes he finds desirable as a policy matter,” and show-it-to-me-in-black-and-white originalism, in which judges interpret the Constitution “when an important originalist principle isn’t set out explicitly but emerges from the Constitution’s structure.”

Another off-ramp, Icarian originalism, occurs when an originalist judge makes the mistake of flying too close to the legalistic sun and thereby loses sight “of what constitutional text would have meant to ordinary people when those provisions were adopted.” Here, Alito cites the “due process” argument within the egregious Obergefell decision of 2015: “For an originalist, the question presented in Obergefell was whether the term ‘liberty’ was understood to include the right to legal recognition of a same-sex marriage. It is impossible to maintain that the general public or lawmakers in 1868 understood the amendment as requiring states to recognize such unions. Yet that’s what the brief argued.”

In the end, Alito believes that originalists need to have steel in their spines because they’ll always be required to make tough legal calls in the face of leftist hostility: “Originalism disciplines the decision-making process, but it doesn’t eliminate the need for judges to exercise judgment. Originalist judging requires a degree of humility, but it also demands boldness to go where the original public meaning leads, and self-confidence in the face of a hostile media and legal academy. So originalism isn’t easy. But if originalist judges stay on course, I am confident that the theory has a bright future.”

Justice Sam Alito won’t be with us forever, so we should enjoy and be thankful for him for as long as he’s on the Supreme Court.