What Can We Learn about Vaccine Hesitancy from Enlightenment Philosopher David Hume?

Fear of needles plus motivated reasoning can lead us in the wrong direction

"Hypodermic syringe 3" by hitthatswitch is licensed under CC BY-NC-SA 2.0

David Hume, the great Scottish skeptical philosopher, died 20 years before Edward Jenner inoculated a 13 year-old-boy with cowpox at the end of the 18th Century. Even though he had never heard of vaccination, Hume’s philosophy has a lot to teach us about vaccine hesitancy in the 21st Century. He famously broke with other Enlightenment philosophers, who put reason and rationality at the heart of their worldviews. He wrote that “reason is, and ought only to be, the slave of the passions.” What does this mean?

Hume had noticed that human beings only pretend to be rational. Instead, our emotions lead the way. Our brains are then very good at rationalizing the conclusions we have reached emotionally. This great insight into human nature has received strong support in the psychological literature since then and is now known as motivated reasoning. It is a central plank in the work of a contemporary writer called Jonathan Haidt.

To see how motivated reasoning works in practice, let’s game out an example. Most of us feel a little queasy about syringes, for obvious evolutionary reasons. Until Jenner made the first breakthroughs that led to modern vaccination in 1796, there was no upside to letting strangers stab you and put substances into your blood. However, there would have been plenty of potential downside!

The thought of injections still makes most of us flinch, even though the benefits now outweigh the risks in a medical environment. Many of us can’t even look at a syringe as it enters our arm. This is all fine, of course, but motivated reasoning means that we will always be tempted to rationalize our fear of needles.

“Maybe the vaccine is too strong? It might make us infertile! Or maybe it is too weak? We might need booster shots every few months, turning us into slaves of Big Pharma! Or maybe it is a secret plot by Bill Gates to inject microchips into our blood?”

While these first guesses might seem contradictory, ill-informed or just plain silly, it is interesting to note an important point: They all follow the grain of our emotions! Actually setting a date with a nurse to receive a vaccination is scary and goes in the opposite direction, even if it is the right thing to do.

Motivated reasoning can be a slippery slope. If you start freaking out about vaccines, you are likely to start rationalizing the risks of COVID-19, telling yourself that it isn’t such a big deal after all. “I have a strong immune system. And, anyway, someone on the internet says there is a magic potion that can cure it.”

The risks of COVID are very clear if you have been trained to deal with large numbers and exponential growth. If you rely on anecdotal experience, the numbers can easily mislead you, making you too complacent. The same is true if you have a conspiratorial mindset or you like hedgehog-like explanations or if you find yourself falling in love with the narratives of gurus, con artists or denialists.

What happens when your friendly neighbourhood skeptic tells someone who is freaking out about vaccines that their magic potion isn’t so magic after all? “The research that claimed to show that ivermectin is an effective treatment appears to be based on a fraud.”

Long-time readers of Sharpen Your Axe will easily guess the answer. Our vaccine-hesitant friend will experience massive cognitive dissonance and double down on his or her starting position. It is very hard to win this argument. Your friend might not have the research skills to recognize information that contradicts his or her emotions. Being too heavy-handed can be counter-productive, even if your friend is mistaken.

Of course, it is important not be too smug, even if you are fully vaccinated. Hume taught us that motivated reasoning is universal. You do it, I do it, we all do it. We shouldn’t judge others too harshly for something we also do.

One of the key lessons of Sharpen Your Axe is that thinking about your methodology is one of the best ways we have of being able to overcome a bad starting position. We need to learn to suspend judgement on our first guesses, then try and work out the probabilities on a sliding scale. Doing this will give us a chance of becoming less wrong, but only if we are absolutely honest with ourselves and with the material. See you next week!

Sharpen Your Axe is a project to develop a community who want to think critically about the media, conspiracy theories and current affairs without getting conned by gurus selling fringe views. Please subscribe to get this content in your inbox every week. Shares on social media are appreciated! If this is the first post you have seen, I recommend starting with the critical-thinking rabbit hole.

[Updated on 10 March 2022] Opinions expressed on Substack and Twitter are those of Rupert Cocke as an individual and do not reflect the opinions or views of the organization where he works or its subsidiaries.