The new president of the Federal Reserve Bank of Minneapolis, Neel Kashkari, has gotten off to a bold start. In a speech this week, he warned that almost eight years after the financial crisis, the largest U.S. banks still pose a grave risk to taxpayers and the broader economy. Dealing with this problem, he said, will require a “transformational restructuring.”

He's right that the financial system needs further reform, and it's good that he's open to radical proposals. But one thing should be clear at the outset: The best way to make banks safer is also the simplest. Require them to finance themselves with more capital and less debt.

Kashkari played a central role in the U.S. Treasury's efforts to shore up the financial system in 2008. He knows the terrible choice that policy makers faced: rescue big banks at taxpayer expense, or risk a worse disaster. He's convinced that—despite the complex panoply of rules and mechanisms put in place since then—the government will be in much the same position when the next crisis happens.