Coronavirus, Correlation & Causation

Martin Jenkins uses the virus to test our knowledge of causation.

- Martin Jenkins

Because of the coronavirus, the skies are bluer, and my vision has improved.

Do those assertions sound crazy? Well, they probably do; but I can demonstrate that they are, if not literally true, logically justifiable. It is an undoubted scientific fact that one result of the lockdown was a severe reduction in travel – both flights and on the ground. As a result, pollution levels have dropped significantly, and so the sky is bluer than usual for want of haze. Also, that lack of haze means that I can look out of my bedroom window, and, for the first time in thirty-four years, see clearly to the horizon –in my case, several miles away in north London. So my vision has improved, in the sense that I can see further than I used to.

Now if we choose to be pedantic, it could be said that these effects are not caused by Covid-19 but by our response to it. But on the other hand, if Covid-19 hadn’t happened, our response of less traffic would not have happened, and so the effects would not have happened; so the effects lie at the end of a chain of causation which begins with Covid-19. In other words, without Covid19, these things would not have happened, so it is legitimate to describe Covid-19 as (in some sense) the cause of these effects.

Human beings are not particularly well equipped to understand causation. We tend to think in post hoc, ergo propter hoc (‘after that, therefore because of that’) terms. C.S. Lewis came up with a brilliant counter-example. A signal sounds in a quarry to announce an explosion. Does the signal cause the explosion? Of course not. But, does the explosion cause the signal? Well, yes, in a sense… But how can something that happens after an event