Leonardo da Vinci was famously secretive about his work, encoding his calculations and experiments for fear, presumably, of being ripped off before he could offer them to his patron of the day. What goes on in our own heads and in our own notebooks remains privately ours until we choose to publish or otherwise offer for money the unique knowledge that we possess.
But who then owns that knowledge? It's an issue of patents and copyright constantly being re-examined as individuals of talent and application need their work funded by universities, foundations and other worthy institutions. I recall that in a moment of madness some years ago, the BBC had the idea of laying claim to every programme idea that passed through the heads of its short-term contract staff. They were not free, it was suggested, to have a programme idea in the months they worked for the Beeb, and then hawk it around the marketplace the moment their contract was up. It was soon obvious implementing such a notion would require something approaching brain surgery to check out the thoughts of such cheating scallywags.
Ideas remain our own, but we like to think that once they are published they belong to the world. Well, not quite, they don't. Currently blowing in from different directions are two matters of money and accessibility that threaten to narrow the scale to which knowledge belongs to us all. First comes the furore swirling around the threat that the British Library may have to charge for the use of its reading rooms.
That such an idea can be even countenanced in one of the world's greatest libraries, an institution hallowed and used by scholars from across the world, is a sad comment on a culture that now views such a dazzling cultural icon as an asset to be traded like so many stocks and shares.
Besides, the books already belong to us - all 10 million of them. The British Library has the right of legal deposit of every book published in Britain. A visit to any of its reading rooms is to enter a world of focused learning, a silence unlike any other, where the only sound might be the hum of hundreds of brains.
There is a hushed concentration that verges on the meditative. It has the feel of a secular cathedral. And its congregations are not the monied classes who could afford to pay. Most of them, whenever I'm there, seem to be young people with the bearing of those keen to learn. It is an oasis for thought that serves everybody, a universal good.
So, too, is our network of free public libraries, among the greatest glories of British culture history. They are one of the institutions we took with us across the empire of which we can be unqualifiedly proud. The British Library was set up in the public's name, its lavish 1998 building paid for by the taxpayers and its storage, services and staff paid for by the state. Like all other such institutions in what's now called the cultural sector, it is having to contemplate a cut in funding because of what is widely known as the Olympic effect, a tag the Department for Culture Media and Sport struggles against all odds to repudiate.
In the case of the British Library, such cuts threaten to do more than pare away any excess fat, but strike at the health of the body itself, the principle that knowledge is there for all to share. Meanwhile, in the EU, a conference will be held next month to debate the matter of "open access to research". European cultural commisars will be in attendance, and have been under pressure recently from the publishers of lavish and expensive scientific journals where such research findings are regularly published.
Scientific journals have become big business, worth some £5.6bn a year. Indeed, academic societies often rely on such publications to keep them going. Perhaps that's why the cost of such journals has escalated so steeply in recent years, as they reserve to themselves the right to distribute new ideas.
But the truth is, those ideas have already been paid for. Many public funders - the Economic and Social Research Council is just one - demand that their researchers place copies of published articles on the web where everyone has free access to them. A year ago, the European Union published a report suggesting they do the same. There is now a call to support such a move. 12,000 academics, including two Nobel laureates are petitioning the European Commission to that effect. The counter-argument is that, starved of their income, many worthy academic magazines would fold. But it cannot be the purpose of the EU to keep such publishers in business. Like all publishers - magazines, newspapers, journals - the reality of the web has to be confronted.
Wikipedia is fun, but it is riddled with errors, and not a resource you'd want to reply on. Indeed, the question grows more urgent daily, of who exactly can you believe. We live in a world of distrust, with confidence in police, politicians, journalists at an all-time low. The profile of religions has never been higher, in all the colourful variety of their strange and unverifiable beliefs.
There is a need to hold on to demonstrable truths about the world and beyond that finds expression in research. Without it we are unanchored flotsam adrift in a sea of rumour and make-believe. The British Library's abundance and the EU's research help us towards balance and insight. It's deluded to think their value to our civilisation can be measured in money.