LONDON — President Obama made a good speech in Arizona almost two years ago after a lone gunman — another troubled young American male wielding a semiautomatic weapon — killed six people and wounded many others, including Representative Gabrielle Giffords.

His theme was American reconciliation worthy of the hopes of a nine-year-old girl killed that day. But he also sounded a steely note: “We cannot and will not be passive in the face of such violence. We should be willing to challenge old assumptions in order to lessen the prospects of violence in the future.”

The president has uttered more moving words, and shed tears, since a 20-year-old gunman — having murdered his mother and grabbed her ample arsenal — blasted his way into an elementary school in Newtown, Connecticut, last week and slaughtered 20 children aged 6 and 7, as well as six members of staff. Again Obama spoke of prayer and community. Again he made the vague promise of “meaningful action to prevent more tragedies like this.”

The Newtown slaughter is many things: evil, unconscionable, literally unbearable. Who can look into the innocent eyes of 20 first-graders and execute them? The temptation is to say only a monster, but of course the answer is a human being.

The way to curtail humans’ ineradicable potential for evil is not soaring rhetoric or heartfelt prayer, but effective laws that govern the interaction of citizens in society. The horror of Newtown is a political failure. It is a failure of American will. That will is personified by the president. Michael Bloomberg, the mayor of New York, was right to chide Obama: “He’s the commander in chief as well as the consoler in chief.”

And command he should on gun control. The issue centers on a handful of words adopted 221 years ago. The Second Amendment reads (every facet of it, including the punctuation, is disputed): “A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed.”

This single sentence has become the rickety basis of an ideology backed by the millions-strong gun lobby. It holds that the right of individuals to bear arms is indivisible from the essence of American liberty. Any attempt to curtail that right is somehow anti-American. In this view, the gun becomes guarantor of vigor and democracy: Feeble Europeans cede their rights to Big Government (their new religion) whereas tough God-fearing Americans believe their government should serve them.

Europeans look on in incomprehension. In many respects European and American cultures intertwine. They diverge over guns and God. The United States has more guns and does more God — a sign of vitality and the absence of European cynicism to some Americans, but a dangerous combination in the eyes of Europeans.

What does young Adam Lanza, armed with a .223 Bushmaster semiautomatic rifle, have to do with anything “well regulated,” or with a “Militia,” or with “security,” or with a “free State” or with “the people”?
Nothing.

The Second Amendment cannot be an untrammeled gun license, the passport to the kind of unregulated ownership of weapons that facilitates mass shootings. James Madison had order in mind not mayhem.
Yet, between Obama’s Arizona speech and this massacre, U.S. gun laws have become less not more restrictive. Old assumptions have not been “challenged” but reinforced. The gun culture runs deep.

Ever since his much-criticized remarks about rural folk “clinging to” guns and God — seen as patronizing liberal snobbery — Obama has been passive (his word) on the gun issue. But these 20 dead children in a year of repeated mass shootings demand that he now push hard to make access to guns “well regulated” — through thorough background checks, waiting periods to allow such investigations to happen, referees for would-be buyers, restrictions on the weapons available and whatever legislation really supports “the security of a free State.”

Responsible gun owners would only benefit. The United States would not be turned overnight into Europe by stripping the Second Amendment of the anti-historical confabulations that have made life far more dangerous for America’s children than it need be.

When young children are slaughtered en masse, it is a moment of reckoning for any society. To dismiss this as the act of a madman is unacceptable when it forms part of a pattern, part of a culture. The question to ask is not whether stricter laws would have prevented this but whether current laws and attitudes enabled it.

Even the Nazis struggled with the enormity of slaughtering children. To overcome the psychological barrier in the Baltic states in 1941, they often hired local police or militias to kill Jewish kids. The subsequent gas chambers were designed for efficiency. They were also a means to avoid doing what Lanza did: look doomed children in the eye.

Fine words and lofty prayer pack up like cheap umbrellas in a storm. What is needed is the political resolve to confront a scourge. Newtown has become a decisive test of whether second-term Obama is different. The signs are not good. His Newtown speech did not contain two essential words: guns and laws.