Rio: Imagineering the future
In recent years the Technology, Education and Design (TED) gatherings have attempted to position themselves as the modern world's imaginarium, giving people a view of what's possible when you unleash creativity.
So given the huge issues facing humanity in terms of sustainability, I was interested to see what thoughts the TEDx event on the fringes of the Rio+20 summit might provide.
Organisers laid on a two-day thinkfest in Forte de Copacabana, a former military base at the southern end of this most famous of beaches that (rather fittingly given its use today) saw rebellion against the established order in 1922.
On the way in, we were invited to sample a number of artistic installations on themes of humanity, biodiversity and sustainability - presenting the problems, you could say, in a more graphical way than the dry reports in which the bad news usually arrives.
The rooftop vantage point gave a nice little vignette of this city's two faces - playgrounds of white sand stretching into the distance, and the endless convoys of enormous cargo ships steaming in and out of port, plying the trade that's helping to enrich this giant nation at some cost to its natural environment.
At the TEDx session I went to, Canadian psychologist Gabor Mate gave an insight into the modern human condition based on his work with addicts.
"If the success of a doctor is measured by how long his patients live, then I have been a failure," he said.
His description of addiction is that it concerns the person much more than the substance; many try drugs without becoming addicted, many enjoy a lifelong relationship with alcohol without becoming an alcoholic.
Dr Mate gave an elegant account of his own struggle against addiction - not to a substance, but to buying classical music CDs, on which he'd once spent $8,000 in a single week and (in a previous medical role) left a woman in labour in order to continue shopping.
Given that the Rio summit (and therefore the TEDx event) is concerned with the state of the world rather than the state of someone's psyche, one could sense there the talk was going - and eventually it did.
Stalin, Hitler, Attila the Hun - all were "quite willing to fight wars and kill people to keep power; power is all about emptiness that you try to fill from the outside.
"Let's not look to the people in power to change things, because people in power are among the emptiest in the world... they're never going to change unless we make them."
Next up was Jean-Michel Cousteau, scion of the famous ocean conservation dynasty and now president of the Ocean Futures Society.
He told us how as a kid he used to bunk off school to catch octopi to sell for a few francs, finding them under rocks in the inshore Mediterranean shallows.
Now, you don't find them there anymore, he said.
A number of conservation groups are hoping Rio+20 will lead to some meaningful outcome for the open oceans, which are in a sense our world's final frontier.
While land and coastal waters belong to nations and therefore stand a chance of being looked after, the high seas are another matter - hardly regulated at all, and therefore increasingly exploited and polluted, with no government obliged to do anything about it.
Ocean Futures Society is arguing that 20% of this area should be set aside for conservation.
It's highly debatable whether the politics exist to make that possible - significant governments such as Japan are determined to preserve fishing access that is only regulated on the basis that it's a food resource, while others such as the US see major riches in the future from minerals exploitation.
And on other issues affecting the oceans - climate change, acidification, plastic pollution - meaningful protection needs to start on the land-based sources of the stuff causing the problems.
Nevertheless, the issue is live in the Rio+20 negotiations.
Laurence Kemball-Cook came on stage to talk about the paving slabs he's invented that generate electricity when they're stepped on.
Each green slab contains a light powered by 5% of the electricity. So what you get isn't only current, but the knowledge that a mere footfall can generate it.
They've already been trialled in schools and other public sites, but the biggest installation so far will be at one of the London underground stations in use for the Olympic Games that begin next month.
Will the slabs survive? Will they thrive? In TEDx language - will they inspire?
Perhaps the most impassioned speech of the day came from someone who wasn't actually in Rio but joined in virtually (the power of the networked world and the information society is a constant TED theme) from her home in Canada.
Severn Suzuki - daughter of the renowned conservationist David - went to the Rio Earth Summit 20 years ago as a 13-year-old to ask her elders to sort themselves out.
That 1992 speech was caught in full on video and it's now one of the most frequently viewed YouTube offerings on environment and sustainability.
What I think caught people's attention was the mood. You might imagine that a 13-year-old girl would talk about emotive things like dolphins and rainbows, and talk in pink generics such as "making the world a better place".
Not a bit of it. Ms Suzuki lays into the delegates: "I've come to tell adults you must change your ways... I'm fighting for my future".
She points out that as yet there is no technical remedy that can clean up mercury pollution or PCBs.
"If you don't know how to fix it - please, stop breaking it," she says.
This year, back via webcam holding one of her own children, Ms Suzuki was no less impassioned, though the message carried a strong flavour of frustration and an occasional hint of despair.
"Twenty years after Rio, we haven't come close to achieving the sustainable society we knew we needed then," she told TEDx delegates.
A while back, she stepped away from big-picture campaigning to work on citizen engagement - trying to generate change from the bottom up.
In Canada, at least, it hasn't worked - maybe not in many other places either. Politically, Canada has shifted away from environmental positions, weakening endangered species legislation, backing fuels such as tar sands, and most recently deciding to leave the Kyoto Protocol.
"The collusion between governments and corporations that we've seen in the last 20 years is enough to make anyone lose faith," she said.
But... the next generation demands better: "I'm a parent and I can't afford to be discouraged".
I don't know if Ms Suzuki could hear the applause she received from the TEDx crowd, but it was huge.
As far as I know, none of the government negotiators who will spend the coming few days attempting to patch together an agreement in the official talks were there to hear it.