“China, the European Union and others have been manipulating their currencies and interest rates lower, while the U.S. is raising rates while the dollars gets stronger and stronger with each passing day — taking away our big competitive edge. As usual, not a level playing field…”

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That’s the tweet from President Trump as he approaches the second anniversary of his warning about a false economy. That was on Labor Day in 2016, when newspapermen on the candidate’s jetliner asked him about interest rates. Mr. Trump proceeded to jawbone the Federal Reserve, saying: “They’re keeping the rates down so that everything else doesn’t go down. We have a very false economy.”

At the time, we thought — as we do now — that it was one of the markers of a winning campaign. It drove Secretary of State Clinton crazy, of course. “You should not be commenting on Fed actions when you are either running for president or you are president,” she harumphed — underlining the fact that the Democratic nominee had nothing substantive to say in respect of monetary policy.

What, though, are we to make of the fact that two years after lacing into the Fed for keeping interest rates low, Mr. Trump, now president, is jawboning the Fed for letting interest rates start to rise? Two years ago he tweeted a prediction that rates would have to rise. Now that he is proven right, he complains: “I don’t like all of this work that we’re putting into the economy and then I see rates going up.”

Our own view is that this is an opportunity for Mr. Trump take on the problem of fiat money. That means dollars lacking a definition in law, currency not backed by gold or any other specie. We plunged into the era of fiat money in 1971, when America defaulted on its undertakings at Bretton Woods. By the end of the 1970s, we’d inked an IMF amendment that forbade countries from defining their money in gold.

This issue is bigger than any other the president has focused on: taxes, regulation, the Iran deal, the climate accord, the Jerusalem embassy, NATO, Brexit, even the NFL. Mr. Trump pressed the issue beautifully during his campaign (as did Senators Rand Paul and Ted Cruz). And it exactly addresses the predicament in which Mr. Trump finds himself as he comes up on the halfway point in his first term.

How, after all, do we determine who is at fault? Is it the Fed for raising rates? Or is it the Europeans and Communist China for keeping their rates too low? By what is one to steer? The dollar might look too strong in respect of European and Communist Chinese scrip. It’s actual value, though, is, at a 1,231st of an ounce of gold, about the same as it was five years ago.

Yet step back a generation — to, say, the start of George W. Bush’s administration — and the Federal Reserve’s one dollar note has shed something on the order of 78% of its value. Since the collapse of Bretton Woods it has shed more than 97% of its value. The last thing Mr. Trump ought to do is to become dependent on the kind of false economy that he ran against in 2016.

Far better to open this issue up now, which the president comes so close to doing in, say, his interview with CNBC’s Joe Kernan. Mr. Trump acceded to the presidency at a time when Congress was primed to start work on monetary reform. Were Mr. Trump to take on the leadership of monetary reform, he could, in addition to all else, get some respite from the scandals of the day and secure his achievement on the economy.