A portrait of the delightfully corpulent David Hume.
In 1998 the British medical researcher Andrew Wakefield announced a startling discovery in one of the world’s most prestigious medical journals, The Lancet. He had found that the Measles, Mumps, Rubella (MMR) vaccine seemed to have caused both bowel disease and autism in children.1 This was startling because the MMR vaccine is a widely recommended and administered vaccine,2 and if it did cause autism or bowel disease, that would be a public health catastrophe.
Although the MMR vaccine had been widely studied before Wakefield’s study, his findings still caused quite a stir. Parents of children with autism seized upon the study as an explanation for why their children had inexplicably been stricken by the disorder. Celebrities like former Playboy model Jenny McCarthy championed Wakefield as a public health savior, and vaccination rates fell worldwide.3 The doctor himself ended up as the executive director for an international nonprofit organization working to prevent autism.
So why is Andrew Wakefield not mentioned in the same breath as Jonas Salk, another hero of public health? Why do doctors still recommend the MMR vaccine, given Wakefield’s devastating study?
The short answer to these questions is that Wakefield faked his results. He lied because he was planning a rival vaccine to the MMR and diagnostic test for autism, and he needed a study to support them. He was also paid by a lawyer who planned to sue MMR vaccine manufacturers.4 His study (and press offensive) helped harm public health by discouraging vaccines and providing a false explanation for autism, and he did it for the worst reasons.
This is not a morality tale, however. Andrew Wakefield and his collaborators knew what they were doing, and their failings were ethical ones. A broader concern is that the editors of The Lancet had no idea that Wakefield faked data. They only knew that they were presented with evidence seeming to show that vaccines caused autism and bowel disease. Should they have known better than to publish the study?
There is a philosopher who had a lot to say about this issue. He is David Hume, one of the foremost members of the Scottish Enlightenment, an 18th century movement which included Adam Smith and Robbie Burns.5 Hume was concerned with many things, but what he is perhaps most famous for is his analysis of the issue of causation.
Aristotle, the great Greek philosopher, believed that he could prove something caused something else by setting up an elaborate logical system that made sense to him. For example, in his logical system rocks fell to Earth because they naturally belonged on Earth. Their “belongingness” caused their falling. Francis Bacon, the original British philosopher of science, disagreed and insisted that causation be proven by careful observation of the real world. Bacon would hope to discover why rocks fell by observing enough instances of rocks falling, as well as instances of rocks not falling, and then carefully coming up with a theory about when rocks would fall and not fall.
Hume took a different approach. First, he disagreed with Aristotle entirely. In fact he claimed that there was no such thing as a logical system independent of the real world because all ideas come from interactions with the real world. More importantly, Hume said that the only way to approach whether something causes something else is by observation, but this causation can never be truly known.6 In other words, no matter how many rocks Bacon watched, he would never truly know what caused a rock to fall.
This is a serious claim. Someone like Bacon, had he been alive at the same time as Hume, probably would have been furious at Hume’s audacious claim. But Hume argues that causation is really just two events happening at the same time or one after the other. For instance, if you take a sip of hot tea and burn your tongue, you think, “The hot tea burned my tongue!” Hume would say, “No, you took a sip of hot tea and you burnt your tongue. One does not have to cause the other.”
The obvious response to this is that every time you have taken a sip of burning hot tea in the past, you have burnt your tongue. And so you think that it makes logical sense to say that hot tea burns your tongue. But Hume would still disagree: there is no reason you should be allowed to assume anything from the past. Hume would want a reason that hot tea necessarily burns your tongue, not simply a past connection.
You may argue that this is how you learned everything and it has worked so far. You learned how hot tea burns your tongue by burning your tongue as a child. You learned how to use pencils by playing with them when you were little, making doodles on paper and seeing how the lead left marks. Almost all of your knowledge is composed of these associations you have made, that you did something and something else happened.
In other words, according to Hume, in the end your justification for reasoning from the past is that, in the past, reasoning from the past has worked. You think you can predict that the next time you sip hot tea, you will burn your tongue. In philosophical terms, your only proof of induction (reasoning from patterns) is induction.
The implications of this are quite serious, meaning that science is built on a shaky foundation, and impressions of causation are really just associations. Hume would argue that we have to consider how sure others have been of wrong causations, like tribes who believed their dances caused the rain. Despite all of our advances, there is no way of proving we are not just as mistaken as those tribes about any of our scientific ideas.
Our answer to this problem, according to Hume, is to treat all philosophy as entertainment and to stop teaching it in schools. We cannot take that option. We have to proceed onward, always aware of how shaky our foundations are, putting one foot carefully in front of the other on the rickety, occasionally rotten bridge of induction.
By the standards of induction, the editors of The Lancet should have recognized that Wakefield’s claim was extraordinary. The MMR vaccine has been studied extensively in many diverse populations and there has never been any proof of it causing autism, nor has there ever been any connection shown between autism and bowel disease. Furthermore, autism itself is both of poorly-understood origins and hard to diagnose, facts which Wakefield used to his advantage, but should have given The Lancet pause. As Hume would have it, even the correlation, never mind the causation, was not clear. Finally, Wakefield based his conclusions on twelve children, eight of whom supposedly showed the connection, which is a small study for such a big claim.
Induction is never totally certain in our world. It merely exists on a scale of certainty, as Hume proved. What is certain is that extraordinary claims require extraordinary evidence to be even tentatively believed, and Wakefield made an extraordinary claim with poor evidence. His claims were so extraordinary that they were in fact more tempting to believe than an ordinary claim, which is a phenomenon that Hume was well aware of.7 Nevertheless, the editors of The Lancet should have been on their guard and realized that Wakefield, even if he had not faked his data, should never have claimed that the MMR vaccine caused autism or bowel disease with any degree of certainty. The editors were not on their guard, and medicine and public health have suffered for it.
- Wakefield, A. J., S. H. Murch, A. Anthony, J. Linnell, D. M. Casson, M. Malik, M. Berelowitz, et al. 1998. “RETRACTED: Ileal-Lymphoid-Nodular Hyperplasia, Non-Specific Colitis, and Pervasive Developmental Disorder in Children.” The Lancet 351 (9103): 637–41.
- “MMR Vaccination | What You Should Know | Measles, Mumps, Rubella | CDC.” 2017. Accessed January 25. https://www.cdc.gov/vaccines/vpd/mmr/public/index.html.
- Fallik, Dawn. 2008. “After Vaccine-Autism Case Settlement, MDs Urged to Continue Recommending Vaccines.” Neurology Today 8 (11): 1.
- Wakefield v Channel Four Television Corporation & Anor, EWHC 2410 (2005)
- Wikipedia contributors, “David Hume,” Wikipedia, The Free Encyclopedia, https://en.wikipedia.org/w/index.php?title=David_Hume&oldid=761588480 (accessed January 25, 2017).
- Morris, William, and Charlotte R. Brown. “David Hume.” The Stanford Encyclopedia of Philosophy. April & May 2017. Accessed January 1, 2017. https://plato.stanford.edu/archives/spr2017/entries/hume/.
- Hume, David. An Enquiry Concerning Human Understanding. Vol. XXXVII, Part 3. The Harvard Classics. New York: P.F. Collier & Son, 1909–14; Bartleby.com, 2001. www.bartleby.com/37/3/.
- Ramsay, Allan. David Hume, 1711-1776. Historian and philosopher. 1766. Scottish National Portrait Gallery. https://jeffwillsonline.files.wordpress.com/2016/04/david-hume.jpg
TREVOR KLEE is a Princeton graduate living and working in Cambridge, MA. He currently works as a GMAT, GRE, and LSAT tutor, as well as a philosophy teacher for a Chinese education startup. His other writings can be seen at www.indefensiblegate.com.