The case for dodging cracks in the pavement

It is interesting to consider what would have happened if the Covid virus had emerged in 1921. Or 1821. Or 1521. There would have been no vaccine, for one thing. Treatment would mostly have been worse. In the 17th century we would have blamed the entire thing on Catholics.

But in a few respects, bizarrely, we might have done better. For instance, miasma theory, although technically wrong, might have protected us better against airborne transmission than the early scientific consensus that the disease was spread via droplets on surfaces. A believer in miasma theory might have practised mask wearing (ideally with a large beak), indoor ventilation and outdoor gathering more assiduously than we did. You can see the benign influence of this theory in the design of many large-windowed, lofty Victorian buildings, and in the heroic success of 19th-century sewage projects. Sometimes we are right for the wrong reasons.

Scientific knowledge aims to progress via the survival of the truest. But there is another large body of knowledge which survives not because it is true but because it is empirically beneficial. Much of our instinct takes this form. Seemingly delusional beliefs survive not because they are rational but because the people or groups who adhere to them tend to survive better than those who don’t, or because the benefits of such beliefs become apparent before we can explain the reasoning behind them.

Consider A.A. Milne’s thesis that there is a high correlation between children stepping on the cracks in the pavement and their risk of being eaten by bears. It is unclear where Milne acquired the data to support this assertion, and subsequent studies have failed to replicate the finding.