On Friday 5 July, as we celebrate Wrong! A carnival of human error at Wellcome Collection, historian of science Dr Anna Maerker will be one of the brave ‘stand-up academics’ taking to the stage as part of our Wrongness Cabaret. Here she explains one particular story that fascinates her, and why…
How do scientists know they’re wrong? A traditional view of science suggests that it’s a fairly straightforward process: you develop a new theory, you do experiments to test the theory, and if the experimental results don’t match the theoretical predictions you were wrong.
The philosopher Karl Popper made being wrong a central part of what it means to do science. Science, he suggested, was a way of moving from individual observations (e.g. “this raven is black”) to universally valid statements (e.g. “all ravens are black”). For Popper, scientific statements were statements that were falsifiable: for example, if a single white raven were spotted.
But although being wrong may be a fundamental part of doing science, it can also pose a serious threat to the experimenter – and observations tend to be rather more complex than distinguishing between black and white ravens. Take, for instance, the work of the German hygienist Max von Pettenkofer (1818-1901).
Like many researchers, Pettenkofer wanted to understand the causes of cholera, which decimated the populations of European cities in the 19th century. Just as John Snow had tried to uncover causal factors by mapping cholera outbreaks in London, so Pettenkofer did the same in Munich. He observed that cholera outbreaks seemed to be most common in low-lying, damp areas and concluded that such environmental factors were necessary for cholera to develop its deadly force.
With this theory, Pettenkofer went head-to-head with one of the scientific giants of his era, the bacteriologist Robert Koch. Koch had famously isolated several bacteria, including a small comma-shaped bacterium that he called Vibrio cholerae and postulated to be the cause of the disease. Pettenkofer did not deny the existence of the bacterium, but he insisted that without the right environmental conditions it would not cause cholera. And he was willing to put his life at stake to show that he was right: in 1893, aged 74, he received a sample of Vibrio cholerae from Koch’s lab and drank it in front of a group of colleagues. He subsequently developed stomach cramps and diarrhoea, but he survived.
Who was right? Both Koch and Pettenkofer considered the outcome of this risky experiment to confirm their own position: Koch’s supporters argued that Pettenkofer had indeed developed the symptoms of cholera, while Pettenkofer pointed out that the bacteria had failed to kill him, thus supporting his claim that the presence of V. cholerae was not sufficient to account for the disease’s deathly force. It required many further interpretations and accounts of the experiment, often by Koch’s students and supporters, to establish a consensus that Pettenkofer got it wrong.
Medicine – and history – is a little more complicated than black and white.
Wrong! is at Wellcome Collection on 5 July.