Some of President Trump’s potential nominees to the Federal Reserve Board have expressed sympathy for a return to the gold standard. Conventional monetary-policy experts deride the idea—and not wholly without reason. The gold standard won’t work for a 21st-century monetary and financial system. It is possible, however, to emulate its best features without actually restoring the gold standard.

The idea behind the gold standard is simple: The government promises that if you bring in, say, $1,000 in cash, you can trade it for...