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 inter-related 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, TheWorld 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 hedge fund manager Paul 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.”

Through the stroke of pen on chequebook, 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 towards 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 early20th-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 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.”