Sometimes, when out on a walk, my dog will eat grass, writes Angus Williams.

Sometimes, when out on a walk, my dog will eat grass. I have always confidently assured myself that she is eating the grass to soothe her stomach – which is no doubt upset after she ate something disgusting.

I don’t know why I believe this. Perhaps I once saw a dog be sick after eating grass? Or maybe somebody mentioned it in passing and I never stopped to question it? Many other dog owners apparently believe this, or something similar.

And, you can’t really blame anyone for believing it. It seems like common sense.

But studies have shown it is not true. According to Stanley Coren, a psychology professor who specialises in canines, dogs may just eat grass because they like the taste.

Over the course of the coronavirus lockdown, the government has moved from being “led by the science” to being “guided by the science” and now on to relying on the judgement of its people.

On Tuesday, prime minister Boris Johnson announced his plans for the further easing of lockdown.

He said: “Our principle is to trust the British public to use their common sense in the full knowledge of the risks, remembering that the more we open up, the more vigilant we will need to be.

“From now on we will ask people to follow guidance on social contact instead of legislation.”

The issue with this statement is not whether people do or do not have common sense, it is that common sense cannot prepare us to deal with something like Covid-19.

Common sense equips us to live in the world as we know it. It tells us not to step into a busy road without looking. To put a jacket on if it is cold. Or to take the bins out when they are full.

It does not equip us to avoid a deadly virus that epidemiologists around the world have been struggling to control for months.

Jim Taylor, another psychology professor, defined common sense as ‘sound judgement derived from experience rather than study’.

We have never experienced a pandemic like this before so have no past experience to draw our common sense from.

People in busy centres like Norwich, Ipswich and Bury St Edmunds cannot be kept safe purely by common sense, but by following guidelines based on the findings of scientists working to control the disease.

To one person wearing a face covering all the time while out in public – rather than just when told to – may seem like the right thing to do, while to some others it may not. The same could be said of the new one-metre plus rule. One-metre plus how much?

These are questions that common sense does not equip us to answer, and the stakes are too high to rely on trial and error.

Even our limited experience of disease may not be helpful in this case. This disease upends all that we thought we knew about viruses. Normally we assume that if we have had a virus once we cannot catch it again – hence parents’ apprehension about children getting chickenpox at the right age.

With Covid-19 this does not appear to be guaranteed, meaning that antibody tests are not the ‘game changer’ they were previously touted as.

Johnson is not the first politician to appeal to common sense and he will not be the last. As long ago as 1776, Thetford-born writer and political activist Thomas Paine published a pamphlet called ‘Common Sense’ that spurred the American colonies on to gain independence from Britain. And the phrase has frequently been turned to by politicians of all bents since then.

But at a time like this, taking decisions away from the experts and leaving a nervous population to fend for themselves – with only recourse to a term that can mean so many different things to so many different people – could have disastrous consequences.