Evidence-based medicine (EBM) has been a powerful influence on clinical practice. But one book should make even the most ardent EBM advocates pause. That book is How Doctors Think, by Jerome Groopman (Houghton Mifflin, 2007). Groopman, an oncologist, drew on the work of Daniel Kahneman and Amos Tversky (before both were made famous by Kahneman's own bestseller, Thinking, Fast and Slow). Groopman used his clinical experience to show how easy it was, despite the very best evidence, to be misled by multiple personal biases—most notably the bias of “availability”. Clinicians will often make diagnoses or decisions based on the mental availability of particular pieces of knowledge, including what might be considered as “best evidence”. Groopman punctures easy assumptions that high-quality evidence alone can improve the quality of medical care. Unless doctors are aware of their own informational biases, the possibility of false reliance on “evidence” is not only conceivable, but likely. How Doctors Think should be required reading before any prospective physician is allowed to lay a hand on a patient. Last week, at the annual Rambam Summit in Haifa, Israel, Groopman, together with Pamela Hartzband, deepened the scepticism with which we should approach EBM. Doctors are educated to believe in their scientific appreciation of evidence. But we may not have educated ourselves to appreciate the mindsets that interpose themselves between evidence and our interpretations of that evidence. Based on extensive interviews with physician colleagues, Groopman and Hartzband identified three dimensions of the medical mindset that any doctor (and patient) should be self-consciously aware of as they make clinical decisions. The three mindsets each have two extremes—maximalist/minimalist, naturalist/technologist, believer/doubter. Ask yourself. Are you the kind of doctor who wants to go as far as you can with the latest technology and who believes in the power of that technology to make a difference to the patient? Or are you the type of doctor who thinks that less is more and who is inherently sceptical about claims for new discoveries? Groopman readily admitted to being a maximalist-believer, which probably influenced his decision in the 1970s to choose haematology as a career when bone-marrow transplantation became popular. Hartzband, by contrast, is a self-confessed minimalist-doubter. Their point was that most clinical decisions lie in a grey zone—there is no single right answer for everyone. The important step is less to adhere to some abstract notion of EBM, but rather to think hard about what kind of medical mindset you have. Whether you are a maximalist-believer or a minimalist-doubter will have a larger effect on your clinical decisions than the result of any single systematic review or randomised trial. We see these mindsets at play all the time in today's scientific, evidence-informed medicine. There have been at least four US expert committees ruling on the safety and efficacy of screening mammography—with four different sets of recommendations. There have been three expert committees reviewing the evidence on screening for prostate cancer using PSA—with three different conclusions. So much for science. So much for evidence. What matters more are the mindsets of those “experts” reviewing the scientific evidence. Here is The Donald Trump Promise, according to Groopman and Hartzband. Modern scientific medicine promises the right doctor prescribing the right treatment and the right procedure for the right outcome. It's just impossible. A final word regarding Joel D Kaufman and colleagues from the University of Washington in Seattle, USA. The International Society for Environmental Epidemiology (ISEE) has awarded its prize for the Best Environmental Epidemiology Paper published in 2016 to Kaufman and coauthors' Lancet Article “Association between air pollution and coronary artery calcification within six metropolitan areas in the USA”. The multicentre team, funded by the US Environmental Protection Agency and National Institutes of Health (both targeted for cuts by President Trump), concluded that, “Increased concentrations of PM2·5 and traffic-related air pollution…in ranges commonly encountered worldwide, are associated with progression in coronary calcification, consistent with acceleration of atherosclerosis. This study supports the case for global efforts of pollution reduction in prevention of cardiovascular diseases.” Congratulations.