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Freeman Dyson was a paradox — an unquestionably brilliant physicist and science popularizer who wasn't worried about global warming. More worried about poverty than climate change, he joined others commonly labeled "deniers" in warning that restricting fossil fuels would harm the developing world.

Anyone else who voiced such views would be labeled as anti-science. But Dyson, who died last week at 96, was part of science. Dyson was a math prodigy who could do mental calculations that astonished the other thinkers at the Institute for Advanced Study. As a young man, he solved hard problems that gave him entry into the physics community without the need of a PhD. He influenced young people, including me, with his popular books, such as "Infinite in All Directions," which dealt with human survival after the end of our world, among other things.

There's a clue to this seeming contradiction in an interview I did with him about that last topic, for a story I wrote for the Philadelphia Inquirer back in 1997. Cosmologists had come to the conclusion — still believed to this day — that the universe will expand forever and grow darker and more dismal as everything disintegrates into an aimless haze of particles. To Dyson, this was not the end of the world. It was manageable.

He imagined that humans and other advanced civilizations would harvest abundant solar energy by building a massive light-capturing shell or envelope around their suns — what came to be known as the Dyson sphere.

But what, I asked him, do we do when all the stars collapse to dead cinders?

Not a problem, said Dyson. "We don't need to worry about stars burning out. " For our energy needs, "any high-mass object will do." Gravity, he said, is by far the most abundant source of energy out there, and intelligent life-forms could harness the gravity associated with all those dense dead stars and even the black holes. They could, for example, swing objects around a black hole, using the black hole as a sort of slingshot, and extract energy from the much speeded-up object as it comes back around."It's an engineering problem," says Dyson, and one that shouldn't be too hard for life-forms that by then will have so many trillions of years of evolution and wisdom behind them. There's also the problem of black holes evaporating, a prediction made by British cosmologist Stephen Hawking. Still, this is not the end of the world, Dyson said. "If you continue feeding them, you can keep black holes going forever. It's actually a winning game if we play it right."

These are not the words of a person prone to denial. He'd thought this all through — his survival schemes were compatible with the laws of physics. And so it should come as no surprise that humanity's accidental upsetting of our atmospheric composition was not a crisis, to him, but a challenge.

He'd thought about global warming — and his answer was to plant a trillion trees, which is a conclusion that some climate researchers reached with much fanfare last summer. The experts warn that tree planting is not enough to keep the globe from warming to a dangerous degree, but it's a necessary part of mitigation.

In a fascinating, controversial 2009 profile in the New York Times Magazine, called "The Civil Heretic," Dyson stated that his concern was that measures to limit fossil fuels would hamper development in China and India and keep people living in poverty.

To Dyson, it's a dispute about values. One the one side are environmentalists, who think, as he put it: " 'nature knows best' and that 'any gross human disruption of the natural environment is evil.' "

On the other side are " 'humanists,' like himself, who contend that protecting the existing biosphere is not as important as fighting more repugnant evils like war, poverty and unemployment. Humans, he says, have a duty to restructure nature for their survival."

Whether environmental scientists would agree with Dyson's characterization of them is debatable — many have pointed out that sea-level rise and ocean acidification will not only displace people (many of them poor) but also threaten the food supply. Others might question whether we truly have a duty to restructure nature.

But Dyson's argument that what we do about global warming depends not just on data, but on deep philosophical beliefs, is a point worth discussing. His optimism might not be politically correct, but it shines a bit of light at a time when fear and gloom pervade everything.

In the meantime, the stars aren't predicted to all burn out for another 100 trillion years.

Faye Flam is a Bloomberg Opinion columnist. She has written for the Economist, the New York Times, the Washington Post, Psychology Today, Science and other publications. She has a degree in geophysics from the California Institute of Technology.