Given the generally grim mood of the American public these days, it might seem like an odd time for Barbara Ehrenreich to publish a book called Bright-Sided, in which she levels both barrels at the American propensity for positive thinking. After all, with the economy still inching back from the brink of catastrophe and unemployment near double digits, doomsayers have never been more in vogue. Far from anticipating the next boom, most Americans seem wary of looking beyond their next paycheck. If anything, some argue, what we need now is a dose of hopefulness.

From Ehrenreich’s perspective, though, our current bout of pessimism is at best a long-delayed confrontation with reality. For decades now, more and more Americans have insisted on looking only on the bright side of things. And that kind of pathological optimism, argues the author, is one of the biggest reasons why we find ourselves in our current mess, and why it’s going to be so hard to get out of it in a sustainable fashion. If we seemed to walk into this financial crisis in a confused daze, Ehrenreich insists, it’s because positive thinking has become the opium of the American masses.

“Positive thinking,” in Ehrenreich’s formulation, is more than just motivational mush. It is a specific ideology with a couple of key elements. First, it encourages people to believe that, on the whole, things are pretty good and that they’re getting better all the time. On top of this generic optimism, though, positive thinking adds a crucial ingredient: the faith that “if you expect things to get better, they will.”

In other words, positive thinking emphasizes the individual’s power over circumstance. According to this supremely irrational creed, people’s thoughts can literally shape the world around them: “Negative thoughts somehow produce negative outcomes, while positive thoughts realize themselves in the form of health, prosperity, and success.” This is the world of books like The Secret, of evangelical preachers like Joel Osteen and motivational maestros like Tony Robbins, a world in which thinking makes it so. The problem is that to be a truly successful positive thinker, it isn’t enough to be optimistic in the face of difficulty. You have to go further than that: you need to deny that the difficulties exist, blocking out bad thoughts and focusing only on the good.

There’s a longstanding strain of positive thinking in American culture, which Ehrenreich dates back to the mid-nineteenth century and what was called the New Thought movement (which gave rise, among other things, to Christian Science). In the twentieth century, a similar philosophy flourished in the hands of popularizers like Dale Carnegie and Norman Vincent Peale, whose promises of personal success through glad-handing and an upbeat attitude captivated millions. But it’s really in recent decades, Ehrenreich contends, that positive thinking has moved from the margins to the mainstream, becoming an indispensable part of the workings of the U.S. economy, and fundamental to the way myriad Americans experience the world.

The heart of Bright-Sided lies in that intersection between the cult of positive thinking and the American capitalist system. But the author begins her book in a very different place: namely, among cancer patients.

In 2000, Ehrenreich was diagnosed with breast cancer. And during the years she spent battling the disease, she discovered something curious: the support groups and online communities that exist to help cancer patients seemed to have little tolerance for anger, fear, or doubt. Instead, people were almost militantly positive, unwilling to focus on anything but the prospect of getting better. A handful even expressed gratitude that they had been stricken with the disease, because of the way it had changed them. This might look like the stiff upper lip in action: Why complain if it won’t do any good? But Ehrenreich argues that what these people were really engaged in was a form of magical thinking. They had convinced themselves that if they adopted the right attitude, they would be able to defeat the disease.

As the author sees it, the problem with this approach is not simply that it’s delusional (while there is evidence that things like stress can adversely affect the immune system, there’s no convincing proof that attitude makes a material difference to cancer outcomes). It also discourages patients from asking questions about the efficacy of conventional treatments, and fosters an unwillingness to consider the very sort of environmental factors that may be responsible for the startling jump in the percentage of American women with breast cancer. Paradoxically, it made people more passive, not less, in the face of their disease.

James Surowiecki is a staff writer at The New Yorker and the author of The Wisdom of Crowds.