As I was listening to Al Gore on the telephone, I was thinking: "Uh-oh, the naysayers will have a field day with this one."

    The former vice president was giving me an advanced briefing on the speech that he delivered on Thursday, calling on the United States to behave like a great nation and actually do something real about its self-destructive and ultimately unsustainable reliance on carbon-based fuel for its 21st-century energy needs.

    "I'm going to issue a strategic challenge that the United States of America set a goal of getting 100 percent of our electricity from renewable resources and carbon-constrained fuels within 10 years," he said.

    "One hundred percent?" I said.

    "One hundred percent."

    Mr. Gore's focus is primarily on solar, wind and geothermal energy. His belief is that a dramatic, wholesale transition to these abundant and renewable sources of energy is not just doable, but essential.

    My view of Mr. Gore's passionate engagement with some of the biggest issues of our time is that he is offering us the kind of vision and sense of urgency that has been so lacking in the presidential campaigns. But the tendency in a society that is skeptical, if not phobic, about anything progressive has been to dismiss his large ideas and wise counsel, as George H. W. Bush once did by deriding him as "ozone man."

    The naysayers will tell you that once again Al Gore is dreaming, that the costs of his visionary energy challenge are too high, the technological obstacles too tough, the timeline too short and the political lift much too heavy.

    But that's the thing about visionaries. They don't imagine what's easy. They imagine the benefits to be reaped once all the obstacles are overcome. Mr. Gore will tell you about the wind blowing through the corridor that stretches from Mexico to Canada, through the Plains states, and the tremendous amounts of electricity that would come from capturing the energy of that wind - enough to light up cities and towns from coast to coast.

    "We need to make a big, massive, one-off investment to transform our energy infrastructure from one that relies on a dirty, expensive fuel to fuel that is free," said Mr. Gore. "The sun and the wind and geothermal are not going to run out, and we don't have to export them from the Persian Gulf, and they are not increasing in price.

    "And since the only factor that controls the price is the efficiency and innovation that goes into the equipment that transforms it into electricity, once you start getting the scales that we're anticipating, those systems come down in cost."

    The correct response to Mr. Gore's proposal would be a rush to figure out ways to make it happen. Don't hold your breath.

    When exactly was it that the U.S. became a can't-do society? It wasn't at the very beginning when 13 ragamuffin colonies went to war against the world's mightiest empire. It wasn't during World War II when Japan and Nazi Germany had to be fought simultaneously. It wasn't in the postwar period that gave us the Marshall Plan and a robust G.I. Bill and the interstate highway system and the space program and the civil rights movement and the women's movement and the greatest society the world had ever known.

    When was it?

    Now we can't even lift New Orleans off its knees.

    In his speech, delivered in Washington, Mr. Gore said: "We're borrowing money from China to buy oil from the Persian Gulf to burn it in ways that destroy the planet."

    He described carbon-based fuel as the thread running through the global climate crisis, America's economic woes and its most serious national security threats. He then asked: "What if we could use fuels that are not expensive, don't cause pollution and are abundantly available right here at home?"

    Americans are extremely anxious at the moment, and I think part of it has to do with a deeply unsettling feeling that the nation may not be up to the tremendous challenges it is facing. A recent poll by the Rockefeller Foundation and Time magazine that focused on economic issues found a deep pessimism running through respondents.

    According to Margot Brandenburg, an official with the foundation, nearly half of 18- to 29-year-olds "feel that America's best days are in the past."

    The moment is ripe for exactly the kind of challenge issued by Mr. Gore on Thursday. It doesn't matter if his proposal is less than perfect, or can't be realized within 10 years, or even it if is found to be deeply flawed. The goal is the thing.

    The fetish for drilling for ever more oil is the perfect metaphor these days. The first thing you do when you find yourself in a hole is stop digging.