At long last, senators stand ready to determine President Trump’s fate. Just don’t call them jurors. Neither are they his judges, though their judgment is required. The peculiar vocabulary of presidential impeachment trials does not end there. The Constitution demands that the chief justice of the United States “preside” over the proceedings, yet that term hardly conveys his potential insignificance. “I did nothing in particular,” explained the last person to oversee a presidential impeachment trial, “and I did it very well.”

Chief Justice William H. Rehnquist was too modest. One of his rulings during Bill Clinton’s 1999 impeachment trial illuminated what we need to know as Trump’s trial begins, and why this vocabulary matters so much, including why no amount of irrefutable evidence that the president committed treason, bribery or a high crime is likely to produce his removal.

A single word holds the key. Iowa’s firebrand progressive, Sen. Tom Harkin, raised the issue two days into Clinton’s trial, objecting to the “continued use of the word ‘jurors’ when referring to the Senate sitting as triers.”

Senators had a fundamentally different role to play during an impeachment trial, and different powers as well, Harkin contended. Jurors determine guilt or innocence, ideally having no foreknowledge of the case before them and considering only the evidence presented in their presence. They can’t overrule their judge, revise court rules or end a trial.

Convened to try the president of the United States, the Senate can do all these things, leading Harkin to conclude that “the framers of the Constitution meant us, the Senate, to be something more than a jury.” He quoted Alexander Hamilton’s assertion that in a presidential impeachment, “there will be no jury to stand between the judges who are to pronounce the sentence of the law and the party who is to receive or suffer it.”

Better to call them a “court,” Harkin implored, because “what we do here today does not just decide the fate of one man” or merely assess his deeds. Instead, the Senate decides nothing less than who should be chief executive and commander in chief.

Cutting him off lest he continue what had every appearance of being a long exegesis on constitutional law, Rehnquist nonetheless accepted Harkin’s point. “The Senate is not simply a jury,” he pronounced. “It is a court in this case.”

This was Rehnquist’s first ruling during Clinton’s trial, and his most important. Acting as a court meant senators could decide Clinton’s fate by whatever metric and means they preferred. They could employ any evidence or logic at their disposal, whether offered during the trial or not, and were not required to employ any particular standard of guilt when making their determination. No “beyond a reasonable doubt” as criminal guilt demands, or “preponderance of the evidence” as for civil judgments. Those are meaningless terms when no subsequent court can challenge their choice.

Members of this “court” are also never required to explain the reason for their votes. Ever. Most undoubtedly will. One does not become a United States senator without a certain fondness for the sound of one’s own voice. Yet even credible reports that President Andrew Johnson won acquittal only through bribery brought no hope of reopening or reversing the Senate’s ruling in his 1868 trial. The decision to retain or expel an impeached president is absolute, without appeal and final.

The implications of this vocabulary reveal an impeachment trial’s true purpose, which is not an act of history but rather of prognostication. Criminal trials weigh evidence to determine whether wrongdoing occurred. By contrast, the Senate impeachment court is charged with weighing a president’s worth. Less restrained by rules and due process than a traditional court, it reviews an impeached president’s record not merely to determine whether his actions harmed the people he’d sworn to protect, but instead to ask whether he has proved himself likely to endanger them in the future. After all, the Constitution gives the Senate no means of punishing a guilty president other than to relieve him of his responsibilities and bar him from holding a post of public honor or profit for the rest of his days.

Subsequent courts may try a defrocked president for criminal misdeeds, but the question each senator in this court must answer in the weeks to come is: Is it time for the president to go? Weighing such matters demands experience as much as an ability to evaluate evidence. “Where else than in the Senate,” Alexander Hamilton asked in the Federalist Papers, “could have been found a tribunal sufficiently dignified, or sufficiently independent” of popular political passions, to determine such weighty matters? “What other body would be likely to feel confidence enough in its own situation, to preserve, unawed and uninfluenced, the necessary impartiality between an individual accused, and the representatives of the people, his accusers?”

This is why no standard of evidence or burden of proof binds this unusual court. Judging character and imagining the future are hard and inherently subjective. One senator’s “perfect call” may legitimately sound treasonous to another. Calling the Senate a court thus allows each member to decide Trump’s fate their own way, because in the minds of the framers, senators were less executors of popular will — which resided in the House of Representatives — than guardians of the people’s needs.

With apologies to the representatives and staffers on the House side of the Capitol who sweated every word and clause of their impeachment articles, senators therefore don’t even need to read them. Majority Leader Mitch McConnell (R-Ky.) may be impolitic in announcing his verdict even before swearing his requisite oath to administer impartial justice, but if he believes that the nation is best served by Trump’s continuation in office for reasons beyond those covered in Trump’s trial, he has the constitutional right to do so. By the same token, House managers need not try to insert evidence from Robert S. Mueller III’s investigation or of Trump’s other alleged misdeeds (such as violation of the emoluments clause or campaign finance law) into a trial ostensibly about Ukraine. Senators may of their own volition consider this evidence in determining Trump’s continued fitness for office. A judge in a criminal case may bar jurors from hearing improperly obtained evidence because legal principles matter more than one defendant’s fate, but with the national interest to consider, this Senate court can consider everything.

This is why Trump is likely to remain in office even if irrefutable evidence of treason, bribery or commission of a high crime appears. Senators may know to their marrow that he committed every crime detailed in his impeachment, yet if they believe that the American people would be best served by Trump’s continued service, they may nonetheless justifiably vote to sustain his presidency. At least one-third of this unique court undoubtedly likes the direction he is taking the country. He’ll therefore be guilty, yet acquitted.

And we their constituents need never know whether his supporters in the Senate made that decision out of conviction or political expedience.

So don’t call them jurors. Senators have much weightier matters to consider than mere guilt or innocence. They must instead judge the nation’s needs and whether this president is likely to do more harm than good in his remaining time in office. Don’t take my word for it, or even Hamilton’s. Thank one firebrand senator and a largely ornamental chief justice for making this clear.