Gates photographed at the Bill & Melinda Gates Foundation in Seattle in September

Bill Gates describes himself as a technocrat. But he does not believe that technology will save the world. Or, to be more precise, he does not believe it can solve a tangle of entrenched and interrelated problems that afflict humanity’s most vulnerable: the spread of diseases in the developing world and the poverty, lack of opportunity and despair they engender. “I certainly love the IT thing,” he says. “But when we want to improve lives, you’ve got to deal with more basic things like child survival, child nutrition.”

These days, it seems that every West Coast billionaire has a vision for how technology can make the world a better place. A central part of this new consensus is that the internet is an inevitable force for social and economic improvement; that connectivity is a social good in itself. It was a view that recently led Mark Zuckerberg to outline a plan for getting the world’s unconnected 5 billion people online, an effort the Facebook boss called “one of the greatest challenges of our generation”. But asked whether giving the planet an internet connection is more important than finding a vaccination for malaria, the co-founder of Microsoft and world’s second-richest man does not hide his irritation: “As a priority? It’s a joke.”

Then, slipping back into the sarcasm that often breaks through when he is at his most engaged, he adds: “Take this malaria vaccine, [this] weird thing that I’m thinking of. Hmm, which is more important, connectivity or malaria vaccine? If you think connectivity is the key thing, that’s great. I don’t.”

At 58, Bill Gates has lost none of the impatience or intellectual passion he was known for in his youth. Sitting in his office on the shore of Seattle’s Lake Washington, the man who dropped out of Harvard University nearly four decades ago and went on to build the world’s first software fortune is more relaxed than he was. He has a better haircut and the more pronounced air of self-deprecation that comes with being married and having children who have reached adolescence. But, with the relentless intellectual energy he has always brought to bear on whatever issue is before him, he still can’t resist the jibes at ideas he thinks are wrong-headed. After the interview, his minders call to try and persuade me to not report his comments on Zuckerberg: as a senior statesman of the tech and philanthropic worlds, it doesn’t help these days to pick fights.

There is no getting round the fact, however, that Gates often sounds at odds with the new generation of billionaire technocrats. He was the first to imagine that computing could seep into everyday life, with the Microsoft mission to put a PC on every desk and in every home. But while others talk up the world-changing power of the internet, he is under no illusions that it will do much to improve the lives of the world’s poorest.

“Innovation is a good thing. The human condition – put aside bioterrorism and a few footnotes – is improving because of innovation,” he says. But while ­“technology’s amazing, it doesn’t get down to the people most in need in anything near the timeframe we should want it to”.

It was an argument he says he made to Thomas Friedman as The New York Times columnist was writing his 2005 book, The World is Flat, a work that came to define the almost end-of-history optimism that accompanied the entry of China and India into the global labour markets, a transition aided by the internet revolution. “Fine, go to those Bangalore Infosys centres, but just for the hell of it go three miles aside and go look at the guy living with no toilet, no running water,” Gates says now. “The world is not flat and PCs are not, in the hierarchy of human needs, in the first five rungs.”

It is perceptions such as this that have led Gates to spend not just his fortune but most of his time on good works. Other billionaires may take to philanthropy almost as a mark of their social status but, for Gates, it has the force of a moral imperative. The decision to throw himself into causes like trying to prevent childhood deaths in the developing world or improving education in the US was the result of careful ethical calculations, he says.

Quoting from an argument advanced by moral philosopher Peter Singer, for instance, he questions why anyone would donate money to build a new wing for a museum rather than spend it on preventing illnesses that can lead to blindness. “The moral equivalent is, we’re going to take 1 per cent of the people who visit this [museum] and blind them,” he says. “Are they willing, because it has the new wing, to take that risk? Hmm, maybe this blinding thing is slightly barbaric.”

Gates, aged 25, photographed in 1981 with Microsoft co-founder Paul Allen

Through the stroke of pen on cheque book, Gates probably now has the power to affect the lives and wellbeing of a larger number of his fellow humans than any other private individual in history. The Bill & Melinda Gates Foundation, which he set up with his wife in 1997 and where he has been working since leaving his full-time role at Microsoft five years ago, gives away nearly $4bn a year. Much of the money goes toward improving health and fighting poverty in developing countries by tackling malaria or paying for vaccination drives against infectious diseases. This is nearly half as much as the US government spent on global health initiatives in 2012.

In many ways, Gates was the archetype for the successful tech entrepreneur, the driven nerd who created an industry with little more than foresight and drive. But to the generation of aspiring techno-visionaries who have followed, the arc of his career no longer has the allure it once did, even if his iconic status is assured. These include people such as Peter Diamandis, a serial entrepreneur who founded the X Prize, which in 1996 offered a $10m award for the first private sector organisation that could create a suborbital space rocket. He likes to think big, and his latest brainstorm involves trying to mine minerals on passing asteroids.

According to Diamandis, the Gates Foundation, with its focus on alleviating the suffering of the poorest, smacks of the early 20th-century philanthropy of the robber barons – men such as Andrew Carnegie and John D Rockefeller, who built and then milked monopolies before spending their later years doling out cash to worthy causes. The latest wave of techno-visionaries, he says, is focused instead on creating whole new industries capable of changing the world.

At the height of its powers, the way that Microsoft wielded its PC monopoly to maximise profits from the computing industry made it feared and hated by rivals and start-ups alike. Now, with the PC world on the wane and the company’s leadership and direction in doubt, it is spoken of almost with disdain in Silicon Valley – even though it remains the third biggest tech company based on stock market value, behind Apple and Google.

Gates Foundation project

Partnering with Coca-Cola and Ghana’s health services Coca-Cola is found in the remotest places on the planet. The foundation is working with the multinational beverage company to use their supply chain expertise to help Ghana’s health service improve delivery of vaccines to the most difficult-to-access patients, including more efficient management of refrigeration systems.

Gates fends off questions about Microsoft, though he says – contrary to persistent speculation – that he is not about to step back in to run it as Steve Jobs once returned to revive Apple. He also admits that the company is taking up a much bigger slice of his time than the one day a week to which he signed up after he left. As chairman and a member of the committee searching for a replacement to Steve Ballmer as chief executive, Gates says he still holds regular meetings with some of the company’s product groups and that he expects to spend considerable time working with the next boss after an appointment is made.

To Diamandis’s argument that there is more good to be done in the world by building new industries than by giving away money, meanwhile, he has a brisk retort: “Industries are only valuable to the degree they meet human needs. There’s not some – at least in my psyche – this notion of, oh, we need new industries. We need children not to die, we need people to have an opportunity to get a good education.”

It takes more than money to rid the world of a scourge such as polio – though having buckets of cash certainly helps. Also needed are ambitious thinking, organisational know­how and the ability to bring new ideas to bear on old problems. These are also the kind of things that go into creating a successful technology company. This time around, though, Bill Gates the CEO has had to take a back seat to a less familiar persona: Bill Gates the diplomat.

When the Gates Foundation made polio eradication a priority five years ago, the global anti-polio effort was running into the sand. More than 10 years of progress had given way, at around the turn of the millennium, to a stalemate as vaccination efforts in the countries still harbouring the disease failed to reach the coverage levels needed to push it into extinction. The organisations behind the existing drive – such as Rotary International, the business group that had long led the effort – “had sort of naively assumed it was on track, but it wasn’t”, Gates says. “The idea that business as usual was going to get us there – it had to be broken out of that, because it wasn’t going to succeed. It probably would have been better to just give up than do business as usual. But that would have been horrific.”

Gates seems to relish nothing more than challenging business as usual, often by applying a dose of more ambitious thinking. It was the same impetus that led him to rethink familiar approaches to philanthropy, throwing his money into the urgent pursuit of solutions to big problems rather than attempting a drip-feed of donations that would amount to little more than a Band-Aid. While the foundations started by the likes of Howard Hughes and pharmaceuticals boss Sir Henry Wellcome are still among the handful of the world’s richest decades after their founders’ deaths, the Gates Foundation has been programmed to dole out all its cash and wind itself up 20 years after their deaths.

The instinct to shake up the complacent and challenge the intellectually lazy doesn’t always win Gates friends. Putting his personal money and reputation on the line to eradicate a disease has also risked accusations of vanity – a case of the “ego philanthropy” that can distort goals when the super-rich get involved. Wiping out a disease has only happened once before, when the World Health Organisation declared in 1980 that smallpox had been eliminated. Helping to finance and organise a second eradication would cap the Gates Foundation’s emergence as the most significant private charity in the world of global health. It would also set the stage for the next items on the list of diseases it hopes eventually to wipe out, starting with malaria.

Gates with his wife Melinda, at a meeting in 2011 with members of the Mushar community in Jamsot, near Patna, India

Gates brushes off questions about the merits of the eradication effort and whether other initiatives might be a better investment in terms of the immediate number of lives saved. “Eradications are special,” he says. “Zero is a magic number. You either do what it takes to get to zero and you’re glad you did it; or you get close, give up and it goes back to where it was before, in which case you wasted all that credibility, activity, money that could have been applied to other things.”

Since he threw his organisation behind the effort, polio has been eradicated in India. But it remains rooted in Afghanistan, Nigeria and Pakistan, spilling over sporadically into their neighbours. That these three countries remain among the world’s most difficult to operate in – in Pakistan, the Taliban has taken to bombing vaccination teams, accusing them of being in cahoots with the CIA – provides a clue about why, nearly 30 years after the eradication campaign began, polio persists. Eradication has little to do with making advances in science and technology – though work on new vaccines targeted more directly at the strains of the disease that remain has helped in the fight.

Take one of the biggest challenges to managing immunisation campaigns against polio and other diseases in the developing world: getting vaccines to where they’re required while keeping their temperature in a narrow 2C-8C range to prevent them spoiling. Running the so-called “cold chain” needed for this to happen – from big refrigerators in regional distribution centres to the cases vaccinators carry into the field – requires painstaking logistical organisation. Often, kerosene or other fuels used in refrigeration are in short supply or antiquated equipment fails due to lack of maintenance. According to Gates, problems like these are too low-tech to attract the world’s best brains. “Unfortunately, it’s a very mundane, practical thing,” he says. “It’s not sexy from a scientific point of view.”

A businessman’s understanding of incentives helps. The number of fridges needed is not large enough to provide a profitable market for manufacturers so the foundation has had to make financial commitments in advance. The business model of the vaccine makers gives them little reason to lower their manufacturing costs to make their products more affordable, he adds. Their high costs are more than covered by prices they can charge in the developed world and any mistakes they might make as a result of tampering with their carefully regulated production processes would jeopardise that existing business. “That’s not science – that’s, how the hell do you make 50 cent vaccines?”

Gates Foundation project

Needle-free immunisation The disposable-syringe jet injector (DSJI) is a needle-free immunisation system developed by Path, a non-profit organisation, with funding from the foundation. Using a pressurised liquid stream to push through the skin, it prevents cross-contamination and injuries to medical staff.

Management methods that would be immediately familiar to anyone involved in the fast-moving technology world are also being brought to bear. These include employing the rapid cycle of trial and error that new tech companies engage in before pouring money into a formula that works – a process known as “scaling”, which takes place as they race to capitalise on a new market before rivals emerge.

Apoorva Mallya, a senior program officer who works on country implementation, puts the success in stamping out the disease in India partly down to pouring money into local initiatives that had the potential to be effective across the country, but which were being conducted on too small a scale to make a difference. These included assigning community mobilisers to individual districts and neighbourhoods before vaccination drives began in order to organise meetings of women and overcome distrust or resistance. “We went in and funded them for a massive expansion across India,” he says.

Another method familiar from the tech world involves more effective data collection and analysis. Vaccination drives fail if too many children fall through the net. To get a better understanding of effectiveness, the foundation has paid for teams of researchers to use statistical sampling to see if adequate coverage levels have been reached.

Measurement is also being brought to bear to build a more detailed understanding of how costs are incurred in vaccination drives. Without that data, it’s hard to know where to focus attention to make global health programmes more effective, says Orin Levine, who runs the foundation’s vaccination efforts. “We don’t necessarily differentiate where the costs are in the system yet, so it makes it harder to say an innovation in [a particular area] will be something we really want,” he explains.

This kind of rigour would be familiar inside an engineering-centric company such as Microsoft, where rationality reigns. But in the more chaotic world of global aid, with its loose alliance of government agencies, NGOs and charities – many of them operating with only partial information – it does not pay to assume such disciplines. Learning to work in that world is one of the greatest adjustments.

“The fact that people don’t understand numbers and systems thinking and science and logic, that’s OK,” Gates says – though his famous impatience might belie such a claim. “I only need a half of the people who contribute to really think in a way where I can say, hey, come on, there’s a theory of change here, do you get it, do you get if that piece doesn’t happen, it completely messes up that piece?”

Like many self-made business people, Gates is wary about the ability of governments to deal with some of society’s most pressing problems. Personal experience might have something to do with it. More than a decade ago, his fight with the US Department of Justice over whether Microsoft had acted illegally to defend its PC software monopoly ended in defeat, though a settlement with the George W Bush White House saved the company from the forced break-up that a judge had ordered.

Gates describes himself as a natural optimist. But he admits that the fight with the US government seriously challenged his belief that the best outcome would always prevail. With a typically generalising sweep across history, he declares that governments have “worked pretty well on balance in playing their role to improve the human condition” and that in the US since 1776, “the government’s played an absolutely central role and something wonderful has happened”. But that doesn’t settle his unease.

“The closer you get to it and see how the sausage is made, the more you go, oh my God! These guys don’t even actually know the budget. It makes you think: can complex, technocratically deep things – like running a healthcare system properly in the US in terms of impact and cost – can that get done? It hangs in the balance.”

Gates Foundation project

Creating a vaccine that can survive at room temperature In 2010, the Serum Institute of India, with funding from the Gates Foundation Meningitis Vaccine Project, developed MenAfriVac, the first meningitis vaccine to be pre-qualified by the World Health Organisation for use at temperatures of up to 40C for up to four days. This made distributing the medication in rural areas much easier.

It isn’t just governments that may be unequal to the task. On this analysis, the democratic process in most countries is also straining to cope with the problems thrown up by the modern world, placing responsibilities on voters that they can hardly be expected to fulfil. “The idea that all these people are going to vote and have an opinion about subjects that are increasingly complex – where what seems, you might think … the easy answer [is] not the real answer. It’s a very interesting problem. Do democracies faced with these current problems do these things well?”

Compared with fixing the US healthcare system, the issues of global health and development taken on by Gates’ foundation are, by his own estimate, relatively straightforward. But the work has required him to develop new skills: a willingness to engage with politicians and to develop reserves of diplomacy and persuasiveness. With more than 1,000 staff members and the ambition to shape the broad strategies directed at solving the problems it takes on, the foundation does much more than simply hand over money. It relies on partnerships with a wide range of government agencies and other bodies to have any effect – and that has forced Gates, the uncompromising and impatient tech leader, to apply the human touch.

Workers at the foundation say that he has been closely involved even at a regional and district level in winning the needed political backing. Gates, for instance, says he personally “bonded with” Nitish Kumar, the highly rated chief minister of the Indian state of Bihar, over the latter’s strong backing for vaccination efforts.

Sometimes in the field of global development, however, it is enough simply to be Bill Gates: the fame and wealth work their own magic. “If … I need to go to the Indian parliament and say, ‘Let’s get serious about vaccines,’ then yes – since I’m giving my own money [on a] large scale and spending my life on it and I’m a technocrat – yes, that can be quite valuable.”

If this brand of international development diplomacy has required new skills, however, some things haven’t changed. Talk to almost anyone who has worked with Gates and they have a story about his intensity. On trips to the developing world his tirelessness wears out those around him. Inside the foundation, he shows the kind of endurance that once inspired and exhausted Microsoft product managers. “He wants to do the work with us at the most granular level. He will sit in four-hour meetings with us going over slide page after slide page,” says Raja Rao, who heads the foundation’s work on perfecting the cold chain. “I’ve seen him sit in a room for 11 hours nonstop just talking about technology, eating snacks and drinking Diet Coke.”

Gates Foundation project

Re-thinking the child health record Paper health records are one of the most reliable sources of medical information. Yet they are often less useful than they might be: lacking enough space to include all relevant information and made of cheap paper which can disintegrate. In June, the foundation launched the $50,000 Records for Life Contest in search of a more durable format to increase usage and the accuracy of information recorded.

Many of the works on the bookshelves in Gates’ office overlooking Lake Washington are scientific tomes on the diseases that he is combating – of which, with characteristic diligence, he now has a deep personal understanding, according to others at the foundation. A voracious reader – he has always taken periodic breaks from his regular routine to read about and ponder the biggest problems he has taken on – his conversation is littered with references to authors. Given the smallest excuse, he plunges into a description of the different types of polio and vaccines – and then into the genetic tests that show how the disease once persisted and spread in areas like Uttar Pradesh even when full outbreaks were rare.

This is the Gates who once ruled Microsoft with a command of detail and intellectual intensity that led to the kind of culture that was capable of dominating the tech world – even as it tipped over into behaviour that brought a regulatory backlash. “I was a kind of hyper-intense person in my twenties and very impatient,” he says. “I don’t think I’ve given up either of [those] things entirely. Hopefully it’s more measured, in a way.”

If the manner has mellowed, though, the uncompromising attitude is still very much in evidence. It is at once one of the strongest assets and one of the biggest hindrances in his plan to save some of the world’s poorest from the fate to which a sometimes oblivious world has left them. Knowing how to pursue an unflinching personal logic without alienating people remains a work in progress for him.

“When we had a meeting a couple of years ago, when people weren’t thinking through the polio thing very well, I was pretty critical,” he says. His message to the assembled workers: “‘Hey, this is not good thinking, this is not good, this is not going to get us there.’”

The new Gates, though, was not prepared to leave it at that. After the meeting was over, he did what husbands the world over are liable to do at such times: “I said to Melinda, was I too tough on that, who should I send mail to, was that motivational, de-motivational? It’s all a matter of degree.”

Richard Waters is the FT’s West Coast editor.

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This article was amended on November 4 2013. An argument forwarded by Australian moral philosopher Peter Singer was wrongly attritubted to hedge fund manager Paul Singer.