With his famed utterance that everyone is entitled to their own opinions, but not their own facts, the late Daniel Patrick Moynihan had to have known, on some level, that he was offering a cliche destined to last the ages.

But the truth, like history, and so many other things these days, just ain't what it used to be.

We live in age, mind, that "alternative facts" are so much in ascendance that it is possible, as the Economist observed, for the president of the United States to both admit - and the later deny - that his was the voice on the notorious "Access Hollywood" video boasting of grabbing women by the "p***y," and having his way with them.

The idiocy, of course, is by no means limited to one side of the political spectrum or the other (though it can be argued, persuasively, that the current White House, with its preponderance of falsehoods, dominates the market on post-truth). The left suffers its own excess, not least of which is the pseudo-science peddled by such Hollywood celebs as vaccination-denier Jenny McCarthy

Still, along come the folks at the RAND Corporation, who glumly remind us in a new report that the nation has come down with a severe case of "truth decay," hastened, among other things, by the 24-news cycle and the ongoing blurring of the line between news and opinion.

"The most damaging consequences of Truth Decay include the erosion of civil discourse, political paralysis, alienation and disengagement of individuals from political and civic institutions, and uncertainty over national policy," authors Jennifer Kavanagh and Michael D. Rich conclude, reinforcing what most of us have figured out already after years of watching the air go out of our national policy debates like so many spent balloons.

The case that Kavanagh and Rich argue echoes one made last summer in "The Death of Expertise," a slender, but compulsively readable, tome by U.S. Naval War College professor Tom Nichols.

There, Nichols, a former staffer to the late U.S. Sen. John Heniz, R-Pa., persuasively argued that Americans weren't only getting dumber - but that they were increasingly proud of everything they didn't know.

And heaven forbid if you try to talk the ignoramuses in our midst down from their know-nothing ledge. Because then you're nothing but a dread elitist.

"The bigger problem is we're proud of not knowing things," Nichols wrote. "Americans have reached a point where ignorance, especially of any public policy issue, is an actual virtue."

So, y'know, go us.

If there's an upside, it's that America has gone through similar periods when truth has taken a beating, the RAND authors note, including the Yellow Journalism of the 1900s and the furor surrounding Vietnam and Watergate.

And, yet, the Republic has still somehow endured.

What makes things different this time, they argue, is that Americans don't agree on the most basic of facts or scientific truths.

"This is to me really a dangerous and unusual time in history. Because Americans not only feel entitled to their opinions--and rightly so--but many of them, a growing number of them, frankly, across the political spectrum also feel entitled to cherry pick facts to support their opinion, or even commission up new 'facts' if necessary," Rich, who's the RAND CEO, observed recently. "... when everyone has their own facts, then nobody really has any facts at all."

And if you've ever been stuck at the dinner table trying to parry your loudmouthed uncle who's seemingly pulling facts out increasingly uncomfortable places to buttress an already batty argument, then you know exactly what he's talking about.

These trends are worsened by accidents of demographics and techology: like-minded Americans marrying each other, and, as a consequence, limiting their exposure to people who might have an alternative worldview; the echo chamber of social media; and our own natural tendency toward confirmation-bias.

The authors offer their own prescriptions to cure what ails us, including, as George Will notes in The National Review this week, the radical notion that schools teach critical thinking, as well as dedicating "public money to support long-form and investigative journalism," which Will pronounces a terrible idea. And I'm with him on that one.

The inability to agree on a basic set of facts goes a long way toward explaining the partisan gridlock plaguing Congress and state Legislatures. And if there's any comfort, it's knowing that, eventually, the pendulum will eventually swing back to normal.

Until then, though, we're going to have to live through an awful lot of toxic nonsense. Hopefully, we'll survive it.