People got up and went to work in London on Friday. They did the same in New York, hopping on subways and buses as always. Stock markets in both countries even climbed above where they were when Thursday’s carnage struck. In short, ordinary human beings on two continents acted with great and silent courage.

Perhaps to a fault.

The counsel that we go about our lives comes from City Hall, the White House and now from heads of state in Europe. Most of us have no choice. We don the uniforms of routine and show up at the office or school or job site to get a paycheck. We try to pretend nothing happened. Or that it won’t happen to us.

But something did happen and pretending could be a fatal mistake. Indeed, too much pretending could bring a sudden end to the world as we know it.

Yes, we must go on with our lives, but we must not become so stoic that we forget the nature of terrorism and what must be done about it. This evil will not go away just because we go back to work.

We face an enemy like none we have ever known. Without warning, they blow up trains and buses, they use airplanes filled with passengers as missiles, they kidnap and behead civilians. These are madmen. They must be wiped out, before they wipe us out.

To the terrorists, 50 or 100 or 500 victims, all that matters is bigger is better. Or have we forgotten the video where Osama bin Laden laughed as he described the twin towers’ collapse? Have we forgotten that each attack is, in his sick mind, a mere warmup to the Big One?

In 1998, he issued a statement titled “The Nuclear Bomb of Islam.” In it, he said that “it is the duty of Muslims to prepare as much force as possible to terrorize the enemies of God.”

His call to duty defines the essence of our duty – that we must be of two minds about terrorism. We must go about our lives as though nothing has changed, while simultaneously remembering that everything could change in an instant more horrible than we can imagine.

Above all, we must not confuse or combine the two ideas. We must not let our courage in everyday life morph into the mistaken belief that terrorists are inevitable or that mutual coexistence is an option.

Sadly, there are warning signs that, as a society, we are falling into that trap. For civilians, the trap lies in thinking that exploding buses and trains are just inconveniences of modern life – and that we can pay such a price as long as the attack is not cataclysmic.

Wall Street even has a phrase for this calculation – the terror risk premium. Certain stocks are priced in anticipation of “events” that will hurt businesses such as hotels and airlines. The hurt, it is assumed, will be temporary. Ergo, the stocks will quickly recover, as they did after Thursday’s “event.”

That’s the business of business. But that’s only half the commitment we need as a society. The other half is an aggressive military and the willingness to use it. We can’t forget that a military on the offense is the national complement to our personal courage of going to work.

Each day in this war is crucial. As President Bush said about bin Laden’s nuclear goal: “He announced that this was his intention, and I believe we need to take him seriously.”

Bush made those remarks almost four years ago, before we went into Iraq. Our mistakes and failures have cost us dearly, there and around the world.

But as the barbarism in London proved, there can be no retreat or compromise in the war on terror. And what Bush said about bin Laden is even more true now: “We need to take him seriously.”