President Trump talks to reporters during a meeting with former secretary of state Henry Kissinger on May 10. (Evan Vucci/Associated Press)

In Martin Amis’s powerful 1991 novel, “Time’s Arrow,” the protagonist experiences his life backward. He is confused by this — patients wait around a physician’s waiting room for an hour after they have seen the doctor — but the device worked for me and just might be the only way to comprehend what is happening in Washington. The Trump administration has reached its end just a moment after it began.

I don’t know if time is going backward or merely being compressed, but the fact is that we are where we would ordinarily not be. Calls are being made for a special prosecutor. There is talk, surely premature, of impeachment. The 25th Amendment, the one that permits the Cabinet to oust a president, is being mentioned. Barely more than 100 days are gone, but they are not like the ones Franklin D. Roosevelt made famous, but an earlier span — Napoleon’s cent jours, from when he left Elba to the day he met his Waterloo at, of course, Waterloo. It is precisely where President Trump is heading.

Trump had ample reason to fire James B. Comey as FBI director. Comey had seriously mishandled the investigation into Hillary Clinton’s use of a private email server while she was secretary of state. At least twice, he crashed through worthy precedent, opining on Clinton’s conduct when it was not his business to do so. He acted as a prosecutor when he was nothing but a cop. He managed, whether intentionally or not, to twice inject himself into the presidential election. Simply stated, that was not his job.

But Trump’s legitimate reasons for firing Comey are hugely beside the point. What ought to matter to the president is that almost no one believes him. His arguments were cogently laid out in a memo written by Rod J. Rosenstein, the deputy attorney general. The three-page document is a head-nodder. You can’t help but agree with each of his points. Yet when the same points are made by Trump, they stink of falseness. He did not want to fire Comey for the right reasons; he wanted to fire him for the wrong ones. He wants the investigation into possible Russian collusion with his presidential campaign to simply go away.

I cannot say whether this is the beginning of the end for Trump. I have frankly thought that the end came at the very beginning, the moment he was elected. He is astoundingly unsuited for the presidency — an ignoramus and a compulsive liar who has seeded his family around the White House like some tin-pot Third World dictator or cinematic creature (Michael in “The Godfather,” for instance). I doubt that the beginning of Trump’s presidency will be the end of his presidency. But everything is backward with Trump. He was elected as a man. But he presides as a child.