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Meg Wolitzer eschews platitudes, shuns homilies and wrinkles up her nose at aphorisms — but without even trying, right out of the blue and definitely off the cuff, she came up with a great definition of novels:

“They’re sort of these … useless essential things.”

She had been trying, during a recent phone conversation from her home in New York, to explain fiction’s place, to justify the space it takes up in our lives, to describe just how made-up stories could compete with inarguably important activities such as earning a living and raising children and making the world a better place.

How dare we write and read fiction, that is, when there’s work to be done? Rallies to join, candidates to elect, whales to save?

And that’s when Wolitzer’s accidental aphorism popped out, the glorious paradox, the one about fiction being pointless — but utterly crucial.

“Fiction, as much as it teaches anything, teaches empathy,” she declared.

Wolitzer’s eighth novel, “The Ten-Year Nap” (Riverhead) will be published Tuesday. As she did in previous novels, such as “The Wife” (2003) and “The Position” (2005), Wolitzer takes a hot-button family and social issue — in this case, stay-at-home moms who relinquished lucrative and high-power careers — and explores it not with charts and graphs and poll numbers, but with plausible characters caught in familiar dilemmas: how to balance work life and home life. How to be satisfied emotionally and spiritually as well as intellectually and financially.

The issue seems to stick stubbornly to women of her generation like the last sock in the dryer, Wolitzer noted: What do you do once the kids don’t need you anymore?

“We grew up with Ms. Magazine. We had big plans for ourselves. Everybody was going full speed ahead.” And then, many of these women — including Wolitzer — had children. They discovered “the beauty and profundity of being with a young child all day long,” she said. “I met women who had had careers but who weren’t burning with ambition anymore.”

However, once the kids start school, once they can tie their own shoes wash behind their own ears, do you then return to the law firm, the accounting office, the boardroom, the newsroom?

“Not everybody loves their work or has a passion for it,” Wolitzer said, whose sons are 17 and 13. “We’ve treated work [outside the home] as if everyone loves it. What if you don’t? I thought, ‘No, there’s a certain kind of woman I’ve met who isn’t necessarily sure what she wants to do when the kids are older, when they don’t need you every second.’ Some women aren’t in a hurry to say, ‘What’s next?’ “

As topical as the theme may be, though, Wolitzer didn’t want to pen an essay. She didn’t want to bang out a polemic. She wanted to write a novel: A big, old-fashioned story with multiple points of view, dramatic crescendos, characters who suffer through long nights of the soul and who, finally, undergo transformations.

“We have to make the case that fiction is relevant,” said Wolitzer, who is married to writer Richard Panek. “I feel like the interior life is always very interesting.”

Wolitzer, daughter of novelist Hilma Wolitzer, said she writes a great deal at night, fueled by Snapple and peanut M&Ms — and a conviction that fiction, even though it can’t halt global warming or save a single spotted owl, still is significant.

“I ultimately want to be stirring in some way,” she said. “I want to have an effect. For me, work is the anti-death. Writing is a way of working out existential problems. I comes down on the side of purpose.”