Experts with opinions and experts with facts

Cecile Janssens
4 min readMar 17, 2020
Photo by Markus Spiske on Unsplash

I have muted the words “coronavirus” and “Covid-19” on Twitter. I hardly see any tweets about the coronavirus epidemic anymore. I would like to stay informed but felt that Twitter was no longer the right medium for that. The line between knowledge and opinion had blurred. I could no longer judge which information I should trust and which I shouldn’t. One scientist tweets that the number of infections is increasing exponentially, the other writes it isn’t. One thinks government measures are going too far, the other not far enough. All experts, but not in this area.

My class on critical thinking last week was about experts and expertise. “Who do you think is an expert on the coronavirus epidemic?” I asked the students of the bachelor’s program in human health. “The epidemiologist?” The first hesitated. The lesson couldn’t get a better start. “I am an epidemiologist,” I replied, “but I know almost nothing about epidemics.”

Expertise is subjective
An expert is someone with extensive knowledge and experience in a specific subject or area. Someone recognized by others for their expertise. An authority. Should someone be a professor or doctor? How many years of experience should someone have? There are no criteria for who is an expert in a particular subject or area. The assessment of expertise is subjective and relative. Someone is an expert, especially when others think they are.

Expertise has limits. An expert specializes in a particular subject, often at the interface of several disciplines. This means that an expert is also well informed on a broader range of topics. My specialization is in the field of predictive DNA tests for complex diseases, such as cardiovascular disease and diabetes. I understand prediction, DNA, testing, and the risk factors for complex diseases, but that does not mean that my expertise covers all those subjects. I may know more about these subjects than the average citizen, but my knowledge on these topics comes with doubts. I can assume that my understanding is correct, but then I am ignoring the limits of my expertise. Someone is an expert on a specific topic, but not outside of it.

So what experts say falls into two categories: topics they know about and topics they don’t know. It is crucial to keep those two apart. When…



Cecile Janssens

Professor of epidemiology | Emory University, Atlanta USA | Writes about (genetic) prediction, critical thinking, evidence, and lack thereof.