The fascinating truth about why common sense isn’t really that common

In the 18th century, philosopher James Beattie compiled a list of 17 common-sense beliefs. A few are incontrovertible: “I exist”; “A whole is greater than a part”; “Virtue and vice are different”. But others seem unnecessarily moralising: “Ingratitude ought to be blamed and punished”; “I have a soul distinct from my body”; “There is a God”. Then, there are the scientifically contestable: “The senses can be believed”; “I am the same being that I was yesterday – or even 20 years ago”; “Truth exists”. Overall, his list seems quaint and outdated. Worse still, it gives no clear idea of what common sense is. Surely, we can do better.

Superficially, common sense seems easy to define: it is generally seen as knowledge or beliefs that are obvious – or should be obvious – to everyone. Yet it is strangely difficult to pin down. Often portrayed as universal, it is also often claimed not to exist. With that in mind, it might surprise you to hear that nobody has tried to measure the “commonness” of this knowledge or its intrinsic properties (its “sensicality”) – until now. Shockingly, this research shows that common sense may not be common at all.

If true, the implications are huge. From parenting to politics and from public health to law, what counts as common sense matters. Increasingly, it is also a technological issue, with computer scientists keen to instil it in artificial intelligence-driven robots to make…