Not many people who want to fix the world think of joining a large corporation. They might imagine volunteering in an orphanage in India, or teaching English in Africa; others might think of becoming a charity fundraiser or human rights campaigner. Some even daydream about getting into the thick of it and becoming a politician.
Big business is more likely to be seen as a part of the problem in the world today, than a potential source of solutions. But that's changing: when we were writing our book, Everybody's Business, we met a new breed of corporate activist, working to change the world from the inside.
As a teenager, Hannah Jones had wanted to fight for social justice. 'In my fantasy, when I was thirteen, I was somewhere between war journalist and campaigning activist, probably scaling buildings with Greenpeace,' says Hannah. Like many people, Hannah thought that the corporates were the bad guys.
So it's a surprise at first to find Hannah working at Nike. But she leads a team improving conditions in the supply chain, and kick-starting innovation that's revolutionising the company's environmental practices. Hannah feels like a woman on a mission: 'At some stage in your life, you have to figure out whether you are more effective shouting from the outside, or whether you can effect change from the inside.'
One of the industries people love to hate is Big Pharma - vilified for aggressively enforcing patents on HIV/AIDs medication, even while millions of people in Africa were dying of the disease. One person who saw this first-hand was Allan Pamba, who was a young trainee doctor in Kenya. It instilled in him a deep anger with the pharmaceutical industry.
And yet today, Allan works at GlaxoSmithKline - the one of the biggest pharma companies in the world. He had wanted to join the United Nations to campaign for health equality, and so studied Public Health at the famous London School of Hygiene and Tropical Medicine. A friend pushed Allan to meet some people from GlaxoSmithKline - and reluctantly, he agreed.
'I thought they were going to be this group of money-hungry, suit-wearing, white men sitting in a room working out how to suck more money off poor patients all the time. I was surprised to find they were just human beings,' he laughs. But what really hit home to him was seeing the possibility that he could influence the company's decisions from the inside.
'I think for the first time it occurred to me that actually it's not a bad idea to be in,' says Pamba. 'If you think there's a need for change, this is a way to create change.' He's been there for eight years now, working on HIV/AIDs treatments and acting as lead physician on the breakthrough malaria vaccine announced this week.
These characters are cropping up in all corners of big business. At Syngenta, a large agriculture business, we found Kavita Prakash-Mani, who has an extraordinary job title: Head of the Global Food Security Agenda. Her job is to identify how the company can make a meaningful contribution to the challenge of feeding a growing population.
Until recently, Kavita was at a not-for-profit think-tank looking at food security. Why did she make the jump into the corporate arena? 'Most of the problems we're all trying to deal with in the global food system today start on the farms and that's where we are - out on the farms,' she tells us, explaining how businesses like hers have a big presence on the ground and a deep expertise focused on improving the yields of small holder farmers who still grow about a quarter of the world's food. 'It's amazing to see that in just a few seasons, you can transform people's lives.'
We met many people like Hannah, Allan and Kavita, intent on fixing the world from deep inside these immense corporations. They're mobilising big business, unlocking the talent and resources of these vast organisations and directing them at the challenges we all face. Of course they're motivated by their own personal success, and the commercial success of their businesses, but they also want to make a real difference in the world.
It shows that the not-for-profit and public sectors don't have a monopoly on fixing the world. At the World Wildlife Fund, veteran campaigner Jason Clay told us how he met Ben & Jerry's founder Ben Cohen at a Grateful Dead concert, and together they developed Rainforest Crunch ice cream - made with nuts from the rainforest. Their plan was to pay three times the market rate for the nuts, thus making it economically viable to leave the forest standing.
It worked. Soon they had had 20% of the global Brazil nut market, pushing up prices across the board - plus earning $100 million in sales for Ben & Jerry. For Jason, it was pivotal: 'It was the first time I saw that it was through business that you have the power to change things,' he said.
Whether inside or outside business, the people we met all shared an energizing point of view: if you want to fix the world, you're better off harnessing the power of business, rather than fighting it. Listening to their stories, you understand that though it can be a tough path at times, it can also be immensely rewarding.
Jon Miller is the co-author of Everybody's Business - The Unlikely Story of How Big Business Can Fix the World, published by Biteback, published this month.