An advertising agency has monopolised, disorganised, and commercialised the largest library in human history. Without a fundamental rethinking of the way knowledge is organised in the digital era, Google's information coup d'état will have profound existential consequences.

Google was originally conceived to be a commercial-free search engine. Twelve years ago, in the first public documentation of their technology, the inventors of Google warned that advertising corrupts search engines. "[W]e expect that advertising-funded search engines," Larry Page and Sergey Brin wrote, "will be inherently biased towards the advertisers and away from the needs of the consumers." And they condemned as particularly "insidious" the sale of the top spot on search results; a practice Google now champions.

Under the sway of CEO Eric Schmidt, Google currently makes nearly all its money from practices its founders once rightly abhorred. Following its $3.1bn acquisition of DoubleClick in 2007, Google has became the world's largest online advertising company. With ad space on 85% of all internet sites, upwards of 98% of Google's revenue comes solely from polluting online knowledge with commercial messages. In the gleeful words of Schmidt, "We are an advertising company." Google is not a search engine; it is the most powerful commercialising force on the internet.

Every era believes their way of organising knowledge is ideal and dismisses prior systems as nonsensical. Academic libraries in the US use subject categorisation derived from Sir Francis Bacon's 17th-century division of all knowledge into imagination, memory and reason. Yet who today, aside from one or two exceptions, would try to organise the internet using a handful of categories? For a generation trained to use Google, this approach seems outmoded, illogical or impossible. But modern search engines, which operate by indexing instead of categorising, are also fundamentally flawed.

Three hundred years ago, Jonathan Swift foresaw the cultural danger of relying on indexes to organise knowledge. He believed index learning led to superficial thinking. Swift was right and a growing of teachers and public intellectuals are coming to the realisation that search engines encourage skimming, light reading and trifling thoughts. Whereas subject classification creates harmony and encourages serendipity; indexes fracture knowledge into snippets making us stupid. Thanks to Google, the superficiality of index learning is infecting our culture, our society, and our civilisation.

Google did not invent the index. That honour goes to the 500 monks led by Hugh of St Cher who compiled the first concordance of the bible in 1230. Nor was Google the first to dream of indexing all of human knowledge. Henry Wheately had the idea in 1902 for a "universal index". And Google was not the first to cynically dump advertisements into the search-engine index. What makes Google unique is the extent to which it has, oblivious to the consequences, made a business out of commercialising the organisation of knowledge.

The vast library that is the internet is flooded with so many advertisements that many people claim not to notice them anymore. Ads line the top and right of the search results page, are displayed next to emails in Gmail, on our favourite blog, and beside reportage of anti-corporate struggles. As evidenced by the tragic reality that most people can't tell the difference between ads and content any more, this commercial barrage is having a cultural impact.

The omnipresence of internet advertising constrains the horizon of our thought. Seneca's exhortations to live a frugal life are surrounded by commercials for eco-holidays. The parables of Jesus are mere fodder for selling bamboo flooring. The juxtaposition of advertisements with wisdom neutralises the latter. The prevalence of commercial messages traps us in the marketplace. No wonder it has become nearly impossible to imagine a world without consumerism. Advertising has become the distorting frame through which we view the world.

There is no system for organising knowledge that does not carry with it social, political and cultural consequences. Nor is an entirely unbiased organising principle possible. The trouble is that too few people realise this today. We've grown complacent as researchers; lazy as thinkers. We place too much trust in one company, a corporate advertising agency, and a single way of organising knowledge, automated keyword indexing.

The danger of allowing an advertising company to control the index of human knowledge is too obvious to ignore. The universal index is the shared heritage of humanity. It ought to be owned by us all. No corporation or nation has the right to privatise the index, commercialise the index, censor what they do not like or auction search ranking to the highest bidder. We have public libraries. We need a public search engine.

In 1998, Larry Page and Sergey Brin made a promise: "We believe the issue of advertising causes enough mixed incentives that it is crucial to have a competitive search engine that is transparent and in the academic realm." Now it is up to us to realise the dream of a non-commercial paradigm for organising the internet. Only then will humanity find the wisdom it needs to deal with the many crises that threaten our shared future.