Default: Are there people in Congress who really would do such a thing?

So, you ask, how could the wealthiest nation on earth, the linchpin of global financial stability, really be heading toward a default whose consequences range from the seriously harmful to catastrophic?

For me, the answer lies not in the complexities of 21st century international finance, but in the last line of a 19th century drama.

When the aristocratic Hedda Gabler finds herself threatened by scandal, she leaves the room — and a moment later, a shot is heard. Judge Brock, the family friend whose behavior triggers her suicide, exclaims: “Good God — people don’t do such things!”

For generations, that conviction has been at the heart of our assumptions about how the American political system works. It’s a conviction that is and has for some time been “inoperative.”

Consider: Since the 1968 elections, divided government has been the norm, not the exception, in Washington. For 32 of the past 44 years, the House of Representatives has been controlled by one party, while the White House has been held by the other. For 22 of those years, the opposition party also controlled the Senate. And for just about all of that time — save only Newt Gingrich’s short-lived shutdown of the federal government — the party that held congressional power played by universally understood rules:

— When a law was passed, however controversial, that law was not subject to endless relitigation. In 1993, President Clinton’s tax and budget measures passed both houses by a single vote; not a single Republican in the House or Senate voted for it. But when the GOP won both houses in 1994, the party did not seek to undo the Clinton tax hikes on the most affluent of Americans. Legislators did not do such things.

— The power given to Senate minorities was to be used sparingly. In 1991, the Senate, in Democratic hands, confirmed Clarence Thomas’ nomination to the Supreme Court by a 52-48 vote — the narrowest confirmation ever. Had opponents chosen to filibuster the nomination, it could easily have blocked the nomination; but the prospect was never seriously raised. Senators did not do such things.

— Members of the House and Senate often voted against raising the debt ceiling — Sen. Barack Obama did so back in 2006 — but such votes were pure posturing (as President Obama recently acknowledged). Such votes were never cast when there was a genuine risk of throwing the United States into default. The idea of holding the international economy hostage to a legislative goal was unthinkable: Serious office-holders did not do such things.

So what’s changed? At root, two generations of office-holders have come to put less and less faith in what once were shared assumptions. Sometimes such skepticism has been well-founded; the members of the House and Senate who followed Lyndon Johnson down the road of escalation in Vietnam, and those who followed George W. Bush into Iraq, came away with sharply diminished faith in the wisdom, and in some cases the honesty, of presidential assurances.

Sometimes, the skepticism has arisen from bedrock beliefs that are radically different from those held by “centrists.” For those who embrace the philosophy of the tea party, the issue isn’t that government is inefficient or wasteful — it’s that it is literally “un-American,” subversive, led by a president who is out to undermine our bedrock principles. (If you think this is overstated, listen to one week of Rush Limbaugh and Company.)

Given such skepticism — and that’s far too mild a word — the arguments of economists, bankers and even conservative Republicans carry little weight. The idea that the Republican Party will do the bidding of large financial institutions began to erode almost half a century ago, with the rise of Southern and Western conservatives with little affection for the Eastern financial giants. The specter of disaster from default? Why believe warnings coming from an administration whose president isn’t a “real American”?

A generation ago, maybe even a decade ago, we could assure each other that the looming default was a political shadow play, with no real prospect of actually happening. People didn’t do such things.

They didn’t then. Now, they well may.