What is this feeling that crops up during so many disasters? After 9/11, I began to see how strange a phenomenon it was and how deeply it mattered. After I met the man in Halifax who lit up with joy when he talked about the great hurricane there, I began to study it. After Hurricane Katrina tore up the Gulf Coast, I began to understand the limits and possibilities of disasters.

When I ask people about the disasters they have lived through, I find on many faces that retrospective basking as they recount tales of Canadian ice storms, midwestern snow days, New York City blackouts, fire in New Mexico, the great earthquake in Mexico City, earlier hurricanes in Louisiana, the economic collapse in Argentina, earthquakes in California and Mexico, and a strange pleasure overall. It was the joy on their faces that surprised me.

Disasters are, most basically, terrible, tragic, grievous, and no matter what positive side effects and possibilities they produce, they are not to be desired. But by the same measure, those side effects should not be ignored because they arise amid devastation. Most social change is chosen—you want to belong to a co-op, you believe in social safety nets or community supported agriculture. But disaster doesn't sort us out by preferences; it drags us into emergencies that require we act, and act altruistically, bravely, and with initiative in order to survive or save the neighbors, no matter how we vote or what we do for a living.

The very structure of our economy and society prevents these goals from being achieved. The structure is also ideological, a philosophy that best serves the wealthy and powerful but shapes all of our lives, reinforced as the conventional wisdom disseminated by the media, from news hours to disaster movies. The facets of that ideology have been called individualism, capitalism, and Social Darwinism and have appeared in the political philosophies of Thomas Hobbes and Thomas Malthus, as well as the work of most conventional contemporary economists, who presume we seek personal gain for rational reasons and refrain from looking at the ways a system skewed to that end damages much else we need for our survival and desire for our well-being. But in disaster people come together, and though some fear this gathering as a mob, many cherish it as an experience of a civil society that is close enough to paradise.

Few speak of paradise now, except as something remote enough to be impossible. But what if paradise flashed up among us from time to time—at the worst of times? What if we glimpsed it in the jaws of hell? Many now do not even hope for a better society, but they recognize it when they encounter it, and that discovery shines out even through the namelessness of their experience.

The word emergency comes from emerge, to rise out of, the opposite of merge, which comes from mergere, to be within or under a liquid, immersed, submerged. An emergency is a separation from the familiar, a sudden emergence into a new atmosphere, one that often demands we ourselves rise to the occasion. The word disaster comes from the Latin compound of dis-, or away, without, and astro, star or planet; literally, without a star. In some of the disasters of the twentieth century—the big northeastern blackouts in 1965 and 2003, the 1989 Loma Prieta earthquake in the San Francisco Bay Area, 2005's Hurricane Katrina on the Gulf Coast—the loss of electrical power meant that the light pollution blotting out the night sky vanished. In these disaster-struck cities, people suddenly found themselves under the canopy of stars still visible in small and remote places. On the warm night of August 15, 2003, the Milky Way could be seen in New York City, a heavenly realm long lost to view until the blackout that hit the Northeast late that afternoon.

You can think of the current social order as something akin to this artificial light: another kind of power that fails in disaster. In its place appears a reversion to improvised, collaborative, cooperative, and local society. However beautiful the stars of a suddenly visible night sky, few nowadays could find their way by them. But the constellations of solidarity, altruism, and improvisation are within most of us and reappear at these times. People know what to do in a disaster. The loss of power, the disaster in the modern sense, is an affliction, but the reappearance of these old heavens is its opposite. This is the paradise entered through hell.

Rebecca Solnit is an activist, historian, and writer, and the author of 12 books. This article is adapted from the book,  A Paradise Built in Hell: The Extraordinary Communities That Arise in Disaster (Viking 2009). Rebecca is also a contributing editor to Harper's and a regular contributor to the LA Times and the London Review of Books.