David L. Ulin / Los Angeles Times

“The Lifespan of a Fact” By John D’Agata and Jim Fingal (W.W. Norton, 228 pgs., $17.95)

The key passage in John D’Agata and Jim Fingal’s “The Lifespan of a Fact” comes late in the book, during an exchange on the role of fact in the amorphous genre known as literary nonfiction, or, in D’Agata’s usage, “the essay.” D’Agata and Fingal are arguing about intent, and the extent to which invention ought to be allowed.

“The Lifespan of a Fact” offers an extended debate on that issue between D’Agata — author of “About a Mountain” and editor of “The Next American Essay” — and Fingal, a former fact-checker at McSweeney’s and the Believer. At the heart of their discussion is an essay D’Agata wrote, which later helped inspire “About A Mountain.”

The intent of “The Lifespan of a Fact” is to destabilize us, to play against our expectations, to make us question what we’re looking at, and in doing so, to raise doubts about our assumptions of the world. “(S)ince when,” D’Agata asks, “did a little intellectual anarchy become a bad thing? Since when did we start allowing rules to dictate what is valid in art? Don’t we purposely afford the artist with liberties that aren’t usually allowed in everyday discourse?”

This is where Fingal comes in, a devil’s advocate for the efficacy of facts. From the outset, he pinpoints D’Agata’s elaborations, the descriptions he’s “streamlined,” the dialogue he’s condensed.

As the book progresses, D’Agata and Fingal turn everything around on us, until even our most basic assumptions are left unclear. Who says writers owe readers anything? Or that genre, such as it is, is a valid lens through which to consider literary work?