First came the earthquake, then the tsunami and the fires, and then, over time, a critical decline in belief in a benevolent God.

The Great Lisbon Earthquake of 1755 killed about a fifth of the city’s 200,000 residents and leveled 85 percent of its buildings, including almost every major church — on a church holiday, when they were packed with parishioners. It also shook 18th-century philosophers to the core. “Candide,” Voltaire’s comic polemic against the belief that all was for the best in this best of all possible worlds, was written in the quake’s aftermath, as Voltaire was abandoning any notion of godly oversight of the world’s affairs. The young Immanuel Kant was sufficiently upset to research and write one of the first books ever on the causes of quakes, before he turned to his life’s work of creating ethical codes that functioned in both the presence and absence of God.

Today, the quake, tsunami and, most particularly, the potential of a nuclear catastrophe in Japan should weaken at least one of our own deeply rooted faiths — in our own infallibility. Consider, for a moment, all the systems that the experts said had been rendered safe, foolproof and immune to disaster, and that nonetheless crashed during the past three years. There was the financial system, an assemblage of immense wagers on all manner of things, which an array of mathematicians and economists assured us could not possibly come tumbling down. There was deep-water oil drilling, which the oil companies’ geologists, among others, insisted could not possibly result in a cataclysmic spill. And today, there are nuclear power plants, safeguarded, their engineers have told us, against the oh-so-remote possibilities of meltdowns.

These assurances — at least, most of them — were not given in bad faith. Wall Street’s quants genuinely believed that they had erected a stable system, as did the geologists and the nuclear engineers. The equations were elegant; things penciled out. At long last, humankind had triumphed over risk.

Except when it hadn’t.

What all these wizards did not factor in was that these were all just as much human and social systems as they were mathematical. Behind the equations were human and social assumptions, rooted in such human and social impulses as greed, denial and hubris. The derivatives that the banks’ economists had devised were said to distribute risk so widely that they made the system safe; but in fact, they interlocked risk so completely that they brought the system down. But they also brought the banks such massive profits that few on Wall Street wanted to recognize the risks that economists not in Wall Street’s sway had detected and identified.

What the systemic failures on Wall Street, in the Gulf of Mexico and in Japan should teach us is that the need for active, disinterested governmental regulation is rooted not in any radical impulse, as the American right continually contends, but in a sober, conservative assessment of the human capacity for mistake and self-delusion, not to mention avarice and chicanery. We can underestimate the risks of a particular undertaking, even when we think we have guarded against them. We fall prey to our own sense of infallibility, often as a way to rationalize what is otherwise a risky endeavor. When those risks go bad, the consequences often fall on those who didn’t take those risks themselves, as the millions of Americans who lost their jobs thanks to Wall Street’s follies can attest. This is a concept that libertarians don’t seem able to grasp, which is why the rise of libertarianism within Republican ranks is bad news for food safety, clean air, economic stability and the like.

The market may in time punish bad actors, which is the ostensible safeguard that libertarians prefer to regulation. Yet as the people sealed inside their homes in the vicinity of Japan’s malfunctioning nuclear plant could tell us, untold numbers of innocents may pay a much higher price, more quickly, than the executives and shareholders of offending companies. For that matter, shareholders and non-shareholders alike, all across the planet, may soon feel economic pain as a consequence of Japan’s insufficient precautions.

And yet, the war on regulation in America — backed by Wall Street and such energy-industry leaders as the Koch brothers — rolls on. Before last week’s quake, House Republicans cut funding for training first responders to radiation disasters. Japan, one hopes, should bring an end to such nonsense. It’s time for our own Lisbon moment. We haven’t defeated risk. We haven’t engineered the glitches out of the system. We need some rules, some regs, and a government willing to devise and enforce them.