COVID-19: Faulty Logic, Distorted Perspectives

May 22, 2020

Tom Jefferson, Carl Heneghan

The Lord Bertrand Russel was always critical of induction, the everyday logic which was first systematised by Francis Bacon, first Lord Verulam

According to induction, science could be founded on repeated observations. Particulars observed repeatedly (such as white swans) could lead to general principles (all swans are white). All swans are not white and induction and its limits are particularly dangerous, if ignored.

Russel exemplified the fallacy of induction with an apt if gruesome famous example, that of the inductivist turkey:

“This turkey found that – on his first morning at the turkey farm – he was fed at 9 a.m. However, being a good inductivist, he did not jump to conclusions. He waited until he had collected a great number of observations on the fact that he was fed at 9 a.m., and he made these observations under a wide variety of circumstances, on Wednesdays and Thursdays, on warm days and cold days, on rainy days and dry days. Each day, he added another observation statement to his list. Finally, his inductivist conscience was satisfied and he carried out an inductive inference to conclude, “I am always fed at 9 a.m.”. Alas, this conclusion was shown to be false in no uncertain manner when, on Christmas eve, instead of being fed, he had his throat cut. An inductive inference with true premises has led to a false conclusion”. 

We have already commented on the reliability of the firm predictions of future “waves” of COVID-19, made even by the most senior politicians of some countries. We have shown how the theory of “waves” is grounded on contemporary reading of influenza pandemics, of which only some had “waves”. This first gap in the pattern would probably not be acceptable to Russel’s turkey. He may, however, concede that given repeated observations of the presence of “waves” in some influenza pandemics, their appearance in COVID 19 would be highly likely. This logic, as Russel’s gory example shows, is faulty. It also has a devastating consequence.

Although ARIs are a syndrome caused by a wide variety of known and unknown agents, the narrative of the last half-century has been dominated by just one: influenza. The figure shows that between 1970 and 2019, 67,936 articles with “influenza” in the title were published and indicized by PubMed. Twelve times the 5,502 coronavirus publications over the same period. 

 In 2020 the picture is completely reversed: 13,847 articles with coronavirus or covid in the title against only 16 articles on influenza – a ratio of 865:1. 

A further idea of the distortion introduced by inductive logic is provided by the most important data of all: deaths.

In Italy, as in all other countries in the world, there are no accurate numbers of deaths by influenza. One study analysing excess deaths for influenza over four years estimated the number for 2016-2017 “season” (the highest of the four years) to be 24,981. For Covid 19, we have far more accurate figures from 20 February 2020 to the time of writing: 32,330 deaths.

Our current approach is based on inductive logic and the research agenda is dominated by the herd approach. This leads to a disproportion between the impact of the disease and its research base and our preparedness. 

By now, not even the inductivist turkey would hazard a prediction. 


Tom Jefferson is a senior associate tutor and honorary research fellow, Centre for Evidence-Based Medicine, University of Oxford.
Disclosure statement is here

Carl Heneghan is Professor of Evidence-Based Medicine and Director of the Centre for Evidence-Based Medicine and the Evidence-Based Health Care Programme.
Disclosure statement is here