The very title of Jane Jacobs’ provocative new book, Dark Age Ahead, will seem to many browsers like hyperbole.

Sure, we’re going through some tough times right now, and not just because of the double-whammy of global war and domestic disinvestment. Professions we depend on to keep society functioning no longer maintain their codes of conduct or ethics. The sciences forge ahead, but research is often premised on unchecked and flat-out wrong assumptions about the world outside the lab, making results useless at best and pernicious at worst. Our universities are devoted to ensuring young people have economically competitive credentials, not a meaningful transfer of knowledge between generations. Basic public services are not functioning because we send our taxes to state capitals and Washington, which cruelly divert them from actual local needs. And families are stretched to breaking by rising costs of living and the demands of a car-commuter economy.

All these terrible developments exact great human cost. But do they portend an end to Enlightenment society as we know it? Are we North Americans about to replay the post-Roman Empire era of mass misery and cultural breakdown, when dirty rags were the height of fashion?

According to Jacobs, the answer lies somewhere between quite possibly and absolutely. She identifies the five areas listed above–the professions, science and technology, higher education, responsive government and community and family–as “pillars of our culture that we depend on to stand firm.” Now, she warns, these institutions “are in process of becoming irrelevant, and so are dangerously close to the brink of lost memory and cultural uselessness.” Her book is an extended essay that she deliberately designed to maintain some hope. It aims to identify “downward spirals,” and to serve as a call to brake descent before it becomes irreversible.

Jacobs has set a mighty high bar, even by her own standards. In her four decades of observing, philosophizing and leading activism to shape livable human environments–starting with the landmark 1962 book The Death and Life of Great American Cities–she has always been a bold and persuasive polemicist. She is a popular intellectual of the most extraordinary kind, building forceful insights out of rigorous observation of the world as it actually functions. Jacobs, who started out as a journalist, had the courage to assume that her own conclusions and intuitions are more valid than all the institutional authority of urban planners, economists, and other men of power whose work she has literally sought to tear down.

She has not lost that force of conviction or her powers of observation. In one poignant moment in Dark Age Ahead, Jacobs confesses that she can’t walk as well these days as she used to, so instead of prowling city streets on foot, she does her work from the back of a taxi–which itself leads to fresh observations about traffic jams, and the myopia of poorly trained highway planners. Contrary to a half-century of evidence, she points out, there’s an unshakeable credo in North America that highways improve a city’s speed of transportation. In itself, that faith is perhaps not disastrous. But as she observes repeatedly (and has throughout her career), everything is interconnected. That’s why bad planning deserves as much opprobrium now as it did when Jacobs first started writing about it so long ago.

In Dark Age Ahead, Jacobs documents at least three such consequences. One is the utter social and economic depletion of urban neighborhoods such as South Lawndale in Chicago, where dozens of poor, elderly people died in a heat wave because they didn’t even have a corner drug store to go to for refuge. Second, she repeatedly decries the loss of opportunities for young people to learn organically from contact with adults bearing diverse experiences and expertise. And Jacobs reserves much of her ink for that most intractable of man-made nightmares, the American car monoculture, which–with an assist from housing policies that promote property values over access to shelter–traps families in an unsustainable spiral of work and debt.

Still, we’ve lived with commercial greed, bad ideas, and toxic environments for eternities. So why decide now that our culture and economy could soon fall apart in a spasm of collective amnesia? Here Jacobs does a bit of a bait-and-switch: In the end, she demurs, we may all come out alive, but dumber, poorer, more brutal. Yet she does seize on some powerful historical examples of societies that have made “wrong turns” that proved fatal–and not just Rome. Riffing openly on Jared Diamond’s popular history Guns, Germs and Steel, Jacobs points to a 15th Century Chinese war minister’s decision to ban international trade, which single-handedly eliminated whole realms of practical knowledge from the culture, and ancient Sumer’s headlong plunge into the cement business, which destroyed the land of the Fertile Crescent, as historical warnings. If nothing else, she wants us to remember what may happen to us if we don’t pay attention.

Jacobs’ associative reasoning style sometimes leaps awfully far and fast. In one doozy, a passage about Enron’s accounting crimes careens into another about the potential of using accounting science to calculate the exact cash value of recovered materials extracted from recycled scrap products.

But throughout her guided and somewhat arbitrary tour of institutional decay, much of it gleaned from the pages of major newspapers, Jacobs holds fast to the one polestar faith she has always had: the power of grassroots economics. She is true believer in small-scale capitalism, and she observes its nuances with the all-encompassing attention a naturalist brings to organic ecosystems.

For example, to understand the prospects for fighting the scourge of suburban sprawl, she draws on her own experience as a New York City renter in the 1930s and 1940s. In the Depression, simply by earning $15 a week when millions of her neighbors were unemployed, she had her pick of 20 or 30 apartments to rent (their former residents, she knew, had left, destitute, and doubled up in new quarters elsewhere). Yet during wartime a decade later, with housing production halted even as demand increased sharply, she and her husband had to take in boarders just to make the rent.

She sees the big green backyards of today’s suburbs as similarly pliable under economic pressures (and throughout this book, she points to mass action as the only way to kick toxic cultural and political habits). Zoning laws that keep densities so low that towns can’t sustain public transportation could buckle and give way, she posits, if homeowners become strapped for cash and turn to creative ways to maximize the value of their property–for instance, by building and renting out bungalows in their backyards. If the suburbs are to become denser and more urbanized, she thinks, it will happen out of necessity and ingenuity like that, and not by some decree or master plan.

In the final pages of the book (written, one suspects, as the American war in Iraq heated up), Jacobs gingerly addresses the divide that more directly preoccupies most Western intellectuals writing nowadays about the future of our culture: the rift between fundamentalist thinking and critical reasoning. Though she never says it outright, she implies that Western fundamentalism is primarily a symptom of breakdown of the five beleaguered systems she’s focused on.

Indeed, probably the most valuable contribution of Dark Age Ahead is that it avoids getting bogged in the mighty distraction provided by the Bush crusades and instead focuses us on matters much more central to our problems as a society, as well as on possibilities for reversing them. No matter who’s in the White House, we all share responsibility for those institutions. And many of us have the power ourselves to do something about them.