Not long before he went to the altar of Notre Dame Cathedral in Paris last month and put a pistol to his head and killed himself, the French historian Dominique Venner was contemplating the contagion of revolt that occasionally sweeps around the globe like a pandemic. “How are revolutions born?” he asked.

Despite Venner’s radical right-wing background, the principles he listed in a blog post were not so much ideological as sociological. And as we look at the tumult in the streets from Brazil to Turkey, the ferocious politics of post-uprising Egypt and the sucking wound of the Syrian civil war, I’m struck by a maxim in Venner’s essay that’s so floridly French, it’s hard to utter, unless you’re sitting at Café de Flore in Paris with a cup of espresso and a Gauloise. “The effervescence,” Venner wrote, “is not the revolution.”

Effervescence may mean fizz as in English, but in French it also means excitement or turmoil, and effervescence often wells up when a regime—often caught completely by surprise—suddenly has to face several different conflicts. The fizz is the screw-the-system, we’re-all-in-this-together, down-with-whoever, up-with-whatever part of the process that takes place when the government starts to lose its grip on power and disorder becomes endemic.

You see that in Brazil right now, where a million people turned out to protest Thursday. There was violence, sure, and one person died, but there was samba, too, and the kind of adrenaline rush that comes from massive collective excitement. A lot of people find the effervescence fun in its early stages. But as Chairman Mao famously said, a revolution is not a dinner party. Effervescence doesn’t become a revolution until it’s organized and led by a party or a person, and then things start to get really serious and can get really ugly.

“I think we desperately need this, that we’ve been needing this for a very, very long time,” a clothing salesman told the Associated Press in Rio de Janeiro as throngs of protesters poured through the streets. At 63, he had lived long enough to see several Latin American revolutions, and he offered an analysis that suggested the Catch-22 inherent in all revolts: “On the one hand we need some sort of leadership; on the other we don’t want this to be compromised by being affiliated with any political party.”

The history of revolutions is, in fact, full of people who rode to power on a wave of popular sentiment, then installed themselves as tyrants. The bloody effervescence of the Bastille gave way to Robespierre and then Napoleon; Stalin crushed Trotsky. (George Orwell’s Animal Farm gives as good a blueprint as any for the way this cynical process works.) And we’ve seen it happen recently in the Arab world. The Muslim Brotherhood in Egypt commandeered the enthusiasm of Tahrir Square to put itself in power; the al Qaeda–linked Jabhat al-Nusra has channeled the moral outrage on the streets of Syria to serve its own violent designs.

But the fizz in Brazil and Turkey has yet to go flat, and the excitement and turmoil may well continue to spread across the globe.

What are the “root causes” of all this ferment? Is it the depredations of unfettered capitalism that make people the servants of the market rather than the other way around? Is it a human lust for freedom? Is it Twitter? Or, at the end of the day, are all politics local, even revolutionary politics? In fact the answer could be yes to each of those questions, but even all those factors combined won’t necessarily lead to full-blown revolutions.

If you try to impose a left-right analysis, moreover, you’ll wind up with your head spinning. Left-wingers often identify with beleaguered workers and old socialist or even communist revolutionary movements, but a lot of the effervescence today is on the right and far right.

The Tea Party in the United States still operates within the system, but its base is full of fizz and is a political force. The Occupy movement on the left looks anemic by comparison. The huge protests in France over the last few months were largely the work of Catholic organizers and a loose constellation of conservative forces opposed to gay marriage, gay adoption—and just about anything else proposed by the current Socialist government in Paris. The most intense revolutionary rhetoric across Europe right now is on the far, far right, with the rise of a crypto-fascist party in Greece the most conspicuous example.

The protesters and rioters in Brazil may be from the classes for whom a 10-cent rise in the bus fare is suddenly unbearable, but they are lashing out at a government that grew from working-class roots. In Turkey, the massive outpouring of emotion on the streets comes from minorities, as the embattled and defiant Prime Minister Recep Tayyip Erdogan insists. But that’s just the point. They feel their country—and especially their cosmopolitan metropolis of Istanbul—slipping under the tyranny of a majority that will squeeze them out of a future.

Revolutions do not start simply because people are fed up with the status quo, in fact. Societies are not static. The uprisings begin when people feel cheated by change. And that can happen across the ideological spectrum. It can feed the fury of black-bloc anarchists and the rage of neo-Nazi gangs. It can bring mothers with their babies in strollers out onto the streets and send marchers protected only with handkerchiefs into the clouds of tear gas and the torrents of water cannons.

Since 2011, when the so-called Arab Spring began, pundits have been looking for historical precedents: the fervor of 1989 that brought down the Berlin Wall and the Soviet empire; the student-led revolts of 1968 that swept from the Left Bank in Paris to blood-drenched Tlatelolco in Mexico City and from Prague to Tokyo. Columnist and Nobel Prize–winning economist Paul Krugman recently looked way, way back and wrote about his sympathy with the Luddites, wool workers who attacked the machines putting them out of jobs in 1786 and denounced the system that gave them no place else to go.

But the mother of all contagious uprisings was the wave of revolutionary fervor that swept Europe in 1848. The events of 165 years ago in France, Italy, Austria, Prussia, and elsewhere are mostly forgotten by modern Americans, but “the parallels with contemporary globalization are very obvious,” says Nottingham University’s David Laven, the author of the forthcoming Restoration and Risorgimento: Italy 1796–1870. The people dying at the barricades were artisans who’d seen their livelihoods taken away by new industries and organizations. They were students whose families had made enormous sacrifices to get them good educations, only to discover the promised jobs were not to be had.

Today, says Laven, there’s the same dislocation, the same glut of education and shortage of employment in many of the countries experiencing unrest. “Without the right connections, you stand not a hope in hell of getting a job in Italy or Greece,” says Laven. People start to revolt, he says, when they feel they’ve been done out of “something they thought was their right.”

When governments hesitate in the face of confrontation, unsure whether to institute reforms or smash their opposition, the effervescence grows. “Revolutions take place when there is sufficient repression to create martyrs,” says Laven, “but not sufficient repression to nip the revolutions in the bud.” The proximate causes of rebellions are not so much long-term structural problems, says Laven, but “short-term triggers” that set off explosive emotions.

The self-immolation of a fruit vendor in Tunisia brought popular anger to a boil in his country in 2011; the savage torture, mutilation, and murder of little boys in Syria for the crime of writing graffiti provoked the protests that have now become a civil war; and the bulldozers about to level a park and build a shopping center in Istanbul sparked the public rage that has shaken the Turkish government to its foundation.

But those who dream of revolutions, or who would plot them, should know that they are hard to trigger on purpose. Many a protester has burned himself alive without bringing on an Arab Spring. There was, really, nothing new about torture and murder by the Syrian regime, but there was never before an uprising like this as a result.

When the 78-year-old Venner walked into Notre Dame de Paris with his gun in his pocket, he also carried a note. “I believe it is necessary to sacrifice myself to break through the lethargy that overwhelms us,” he wrote. He could not bear the way France and Europe are changing, could not endure the threat of massive immigration. He had seen the massive anti-government rallies and thought a critical moment had come. By giving up of his life, he could help trigger more protests, a movement, a revolution.

But the Venner suicide only made headlines for a day or so. The anti-gay-marriage protests have subsided, and so has the talk of a new French revolution. Summer is here, people are thinking about vacation, and the fizz has fizzled. France will have to wait for another martyr, another trigger, and that may never come. But other countries may yet find plenty of their own.