You've probably heard by now that Greg Mortenson, the author of Three Cups of Tea, is under fire for allegedly exaggerating or concocting from whole cloth many of the events in his famous book.

Mortenson has become a major force in shaping America's mental picture of itself in an age of permanent war.   We are warriors, his book suggests, but also healers and teachers.

In March 2010, David Sommerstein reported on the profound impact of Mortenson's visit to Fort Drum, near Watertown, to talk with soldiers and families.

"As [military] spouses, we spend so much of our time hoping the phone doesn't ring, finding comfort in each other," said Heather Sutton, one of the organizers of the Watertown event.

"When we read a book like that, I think we automatically need to and want to see the positive."

But on Sunday, the CBS News magazine 60 Minutes reported in depth that many of Mortenson's claims about his own personal narrative and about his school-building work in Afghanistan, are dubious.

It remains unclear whether  he will be able to explain away the apparent discrepancies in his hope-inspiring tale.

But it's worth noting that supposedly well-meaning literary frauds are a fairly common event in our culture, going back hundreds of years.

One of the most interesting cases involves the poems of Ossian.

The poems were supposedly discovered and translated in the 1760s by a Scottish poet named James Macpherson, and they formed a centerpiece of the Scottish independence movement.

Activists snapped up the work, and adopted it as a sort of banner of their worldview.

They needed the hope and identity that seemed to be buried in those lyrics, just as families at Fort Drum need Mortenson's narrative of war-zone idealism.

It turns out the Ossian writings were largely cooked up by Macpherson himself, but that didn't prevent the poems from becoming hugely politically influential.  Thomas Jefferson was a fan, supposedly, as was Napolean.

There was a time when this kind of thing was looked on with less severity.  Here's an account of Benjamin Franklin's often political writing offered during a PBS documentary about his work.

"When Franklin used a pseudonym, he often created an entire persona for the 'writer.' Sometimes he wrote as a woman, other times as a man, but always with a specific point of view."

Franklin often winked at his readers, suggesting that his work was less a con and more a literary device.

But there has emerged in the last half-century a bizarre cottage industry in Holocaust writing, for example, that purports to actually be authentic, first-person accounts of life under the Nazi regime.

Often these deceptive works offer powerful expressions of persecution and identity.

The most famous is probably The Painted Bird, by Jerzy Kosinsky, which was embraced by political figures including Elie Wiesel.

Most scholars now believe Koskinsky's text was not autobiographical but was, rather, a fairly inspired work of fiction.

The personal memoir is perhaps most vulnerable to this kind of fool-me-twice writing.

James Frey's hugely influential account of his own troubled life, "A Million Little Pieces," turned out to be heavily leavened with hokum.

So was Margaret Seltzer's account of life in the gang culture of East LA, which was withdrawn by her publisher when it turned out the work was largely fiction.

The truth, of course, is that the truth matters.

Whether writers are shaping our mental landscape over relatively small domestic things — addiction and recovery, for example — or big things like war and genocide, they can literally change the world.

If Mortenson's account of his own humanitarian work turns out to be accurate, then we know something concrete and meaningful and hopeful about our society's role in Afghanistan, both as warriors and as peace-makers.

But if his account is mostly fiction, then we have learned once again, painfully, that in war truth really is the first casualty.