Imagine yourself in the coffee houses of 18th century Edinburgh, in the elegance of the New Town when it really was new, the civilization of those paved streets, and the intellectual excitement of the Scottish Enlightenment.
It was there that the philosopher David Hume first cast doubt on scientific method, peering at ideas about what causes what and finding there was nothing there. All you can do, he said, is say that events tend to happen together.
Yet, if we can see nothing causing things under the philosophical microscope, that hands the scientists a big logical problem. It doesn’t matter how many times they do an experiment, or watch the sun rising bang on time, it doesn’t mean these events are any more likely to happen tomorrow.
Two centuries after Hume was writing in Edinburgh, the Viennese philosopher Karl Popper, a refugee from the Nazis, came up with an interim answer. But, more importantly, he also applied it to politics and organizations. You may not be able to prove what you believe about the world, no matter how often an observation or experiment takes place, but you can disprove it.
Popper used the example of swans. It doesn’t matter how many white swans you see, it still doesn’t prove that all swans are white. But if you see a black swan, then you know they are not.
Popper was writing during the Second World War, his home city was in the hands of totalitarians, and he quickly found himself applying this insight to politics too. In doing so, he produced one of the classic 20th century statements of philosophical liberalism, The Open Society and its Enemies (published in 1945).
He said societies, governments, bureaucracies and companies work best when the beliefs and maxims of those at the top can be challenged and disproved by those below. This has huge implications, not just for effective societies, but for effective organizations too.
Popper was flying in the face of the accepted opinions of the chattering classes at the time. They may not have liked the totalitarian regimes of Hitler or Stalin, but people widely believed the rhetoric that they were somehow more efficient than the corrupt and timid democracies.
Popper explained why they were not and why Hitler would lose. Anybody who has read Antony Beevor’s classic account of the Battle of Stalingrad, and the hideous slaughter and inefficiencies brought about by two centralized dictators who had to take every decision personally, can see immediately that Popper was right. Real progress required ‘setting free the critical powers of man’, he said.
The possibility of this challenge – in what he called ‘open societies’ – is the one guarantee of good and effective government or management. Those human beings at the front line, those most affected by policy, will always know better about their own lives or their own work than those at the top.
Open societies can change and develop; closed societies can’t. Hierarchical, centralized systems, by their very nature, prevent that critical challenge from below.
Why this rant about Popper? Because he is the critical Liberal philosopher of the twentieth century. I kept saying so during the process that produced the Liberal Democrat philosophy document It's about freedom, but still failed even to get him a name check.
But also because he is the central figure of Nick Clegg's important speech today on the open society to Demos (though again Popper only gets one name check). The speech is vague about Popper, vague about precisely why Popper said open societies work and closed ones grind to a halt, but it chooses exactly the correct philosopher - exactly the right underpinning to make Liberalism distinct now.
It is also, as it happens, the philosophical justification for Liberal-style localism - it is about "setting free the critical powers of man".