In the year 1500, only about 11% of the population could read.¹ And because books were a rare commodity, even those who could read would not read a lot. Most people would be drip-fed information about the world by travellers bringing news by word of mouth.

Today, most of us spend much of our time being fed information: from books, websites, messages, TikTok. We have access to knowledge that a mediaeval peasant could never have dreamt of.

But because we know so much, we probably also believe a lot more that is wrong. We are so constantly deluged with information that we can end up passively absorbing most of it.

And most of it is probably false. Lies get more views than truths. On Twitter, fake news stories are 70% more likely to be retweeted than true ones, and spread six times as fast.²

What can we do about this flood of misinformation? Proposals to put tougher regulations on social media sites have generally fallen through. Search engines have not found a way of dealing with malicious SEOSearch Engine Optimisation. The practice of improving your website to make it more visible on Google or other internet searches. .³

One writer has a different answer: change the way we think as individuals. Alex Edmans is a finance professor whose new book, May Contain Lies, promises to help us sift through the misinformation.

Edmans thinks the reason we are so susceptible to misinformation is that we like having our biases confirmed. When we find a fact or statistic that seems to confirm what we already believe to be true, we generally stop looking, happy in the knowledge that we were right.

He gives an example from his own life: for years he repeated the claim that it takes 10,000 hours of practice to become an expert in something, because it was a useful way of driving home the value of hard work in his lectures.⁴

But when he actually checked the data behind this claim he found it had almost no basis in fact.

He thinks we could solve the misinformation problem if we all just learnt to check our facts and think critically about what we are told, to hold an idea in our heads without automatically accepting it.

But some think this is a fantasy. It would take far too much effort to weigh up everything we know, check the source, cross-reference it with other sources, figure out which sources are trustworthy and which are not. Most people simply do not have the time.

They say it is really a structural problem. The fact is it takes far more work to produce truth than to produce lies. If you want to write something that is accurate it can take days, weeks, months, years of research.

You do not have to do any of that if your aim is to spread fake news, so you can produce much more of it.

Then, as more and more of the internet comes to be made up of poorly-researched false information, checking and cross-referencing information becomes harder.

Someone writes something false and puts it on the internet. Another person finds it, believes it, and puts it on their own website. A third person finds there are two sources repeating the same claim and thinks it must therefore be true, so they write it up as well. And so on.

The average web user does not go past the first five listings of a Google search.⁵ Four of those five websites might have used the fifth as a source. But because they all say the same thing, we will likely believe the information they give us is trustworthy.

Can we train ourselves to be lie-detectors?

Yes: We cannot hope for a world where we can be sure that no-one is lying to us. The only way we can be sure of what we know is if we develop our critical abilities.

No: We live in a specialised world. Most of us do not have the background knowledge that we need to investigate whether complex information is true. This needs a structural solution.

Or... The trick is to know what falsehoods matter. For most of us, it is not the end of the world if our knowledge of chemical reactions is a bit oversimplified. It is more of a problem if we believe false things about politics.