On Wednesday, Treasury Secretary Jacob Lew sent the House a very serious warning that, for the first time, the United States would be unable to pay its bills beginning on Oct. 17 if the debt ceiling is not lifted. House leaders responded on Thursday with one of the least serious negotiating proposals in modern Congressional history: a jaw-dropping list of ransom demands containing more than a dozen discredited Republican policy fantasies.

We’ll refrain from deliberately sabotaging the global economy, Speaker John Boehner and the other leaders said, if President Obama allows more oil drilling on federal lands. And drops regulations on greenhouse gases. And builds the Keystone XL oil pipeline. And stops paying for the Consumer Financial Protection Bureau. And makes it harder to sue for medical malpractice. And, of course, halts health care reform for a year.

The list would be laughable if the threat were not so serious. A failure to raise the debt ceiling would cause a default on government debt, shattering the world’s faith in Treasury bonds as an investment vehicle and almost certainly bringing on another economic downturn. Unlike a government shutdown, a default could leave the Treasury without enough money to pay Social Security benefits or the paychecks of troops.

The full effects remain unknown because no Congress has ever allowed the government to go over the brink before. The Government Accountability Office estimated that simply by threatening to default in 2011, Republicans cost taxpayers $1.3 billion in higher interest payments because of that uncertainty. The 10-year cost of those higher-interest bonds is $18.9 billion.