Uncertainty is uncomfortable. It is only natural to want certainty. It is more comfortable to be certain and wrong than to be uncertain. Like anyone else, I would like to be comfortable, but I think truth matters. I’d rather be uncertain than wrong; wouldn’t you? As Voltaire said, “Uncertainty is an uncomfortable position. But certainty is an absurd one.”
Belief offers certainty but not truth. Your degree of certainly has nothing to do with how right you are. But if people’s false beliefs make them happy, should we discourage them? I think so. Happiness is important, but truth is arguably even more important. And people who accept one false belief are likely to accept others. Critical thinking skills don’t come naturally, but they can be learned. Skeptics trust their hard-earned critical thinking skills; they look for evidence and distrust unsupported beliefs.
Science can be very certain and precise. It tells us exactly when to expect the next total solar eclipse and when Halley’s comet will return. It predicts exactly how much of what compound will result from a chemical reaction when two substances are mixed. It calculates the half-life of radioactive elements and can accurately predict the percentage of atoms of radium that will have decayed to lead-206 in any given time period. It enabled us to land humans on the Moon (and bring them back!).
We have come to trust science and to think of it as a reliable guide to truth. It’s easy to forget that science has been wrong many times. Remember those cold fusion experiments and the many experiments that seemed to show evidence for the reality of nonexistent N-rays? Science once supported phlogiston and the ether. Science can make mistakes, but it has built-in self-correcting mechanisms. It may take a long time, but errors will eventually be corrected, and truth will ultimately triumph. Science is not perfect, but it’s the best tool we have for understanding reality.
We tend to think of medicine as science, but it’s not a science like astronomy or physics. Good medicine is based on science, but it’s an applied science. Treatments are based on evidence, but that means medical advice will change if better evidence comes along. Some people see the fact that medicine keeps changing its mind as a reason to distrust medical advice. But that’s not a defect; it’s a strength. It shows that medicine is responsive to reality.
Uncertainty is ubiquitous in medicine. Memory is unreliable. Patients’ reports of symptoms may not be accurate. Physical exams can miss things, and anatomy is variable. For instance, in situs inversus, the organs are on the “wrong” side of the body. Lab tests are subject to many types of error, from failure to calibrate instruments to simple clerical errors. And normal lab values are a fiction based on testing a lot of people and calling the middle 95 percent of the bell curve “normal.” Imaging studies can be unreliable; remember the MRI study that seemed to show what a dead salmon was thinking? Even genetic testing can be wrong; for instance, the genes of a man with blue eyes indicated that he should have brown eyes. Definitive diagnoses of some diseases may have to wait for autopsy. An antibiotic that is “certain” to cure an infection might not work for an individual if it triggers an allergic or idiosyncratic reaction.
The predictions of science can be very accurate, but what about patients with a terminal disease who ask the doctor how long they have to live? Testimonials for alternative medicines often start with “The doctor said I only six months to live, and I’m still alive three years later thanks to X” (where X is some random bogus remedy). Doctors’ predictions are often wrong, and patients may misremember or hear what they expected to hear rather than what the doctor actually said. Doctors who say “six months” can’t really know if that is accurate. At best, it is only a guess based on the recorded survival of similar patients with the same disease. A median survival of six months doesn’t mean that everyone will suddenly drop dead six months later. It means that some individuals will die before six months and some won’t die until after six months—sometimes long after. And possibly never: spontaneous remissions have occurred even in the most deadly diseases. Spontaneous remissions are not understood and can’t be predicted.
One of my favorite diagnoses is IBTHOOM (It Beats the Hell Out of Me). If doctors are honest, they will admit that they can’t explain everything. I often had to tell patients I didn’t know what was wrong with them. I only knew what was not wrong with them because testing had ruled out those diagnoses. It would not be reasonable to do every possible test a laboratory could offer or to do exploratory surgery or brain biopsies with no idea what we are looking for. I tried to persuade my patients that more testing at this point would be useless or even counterproductive. A wild goose chase might only turn up random false positive results and end up doing more harm than good. I reassured them that if they got worse, we could then do directed testing as indicated for their new symptoms. Meanwhile, we could concentrate on finding ways to help them cope with their present situation. Most patients were happy to accept that watchful waiting was the best option and were open to efforts aimed at mitigation. Note: I retired before alternative medicine became popular, so my patients didn’t have that temptation.
Fantasy can be very seductive, but in the end it’s reality that matters. You could imagine that your cat is a chair, but if you try to sit down on it, reality will intervene. The result will be a cat-astrophe. Your furry friend may be squashed and killed or seriously injured. Or the cat may yowl, hiss, bite, or scratch you—or run away.
Uncertainty is not just a feature of medicine. It is everywhere. According to an old saying, nothing is certain but death and taxes. But maybe even those are uncertain. There are people who deny that death exists; they think there is only a transition to something else. And some people are convinced they have no legal obligation to pay taxes.
Doctors regularly face uncertainty. They constantly have to make decisions based on inadequate information. They have to prescribe an antibiotic before the cultures have identified the pathogen. They may get it wrong, but they have to do something. Doing nothing is not an option; without treatment, the patient will die. When unexpected bleeding occurs during surgery, the surgeon has to take swift action. If he “does a Hamlet” and stops too long to think about it, the patient will bleed out and die.
Doctors have to make educated guesses based on many factors. They have to consider what diseases are prevalent in their community, whether the patient is a reliable historian or has a habit of hysterically rating their pain as fifteen on a scale of ten. Doctors have to judge probabilities and decide whether the test results should change their minds. Is the post-test probability of the diagnosis greater than the pre-test probability? Is there even enough reliable information available to base estimates of probability on? Doctors are constantly having to make informed guesses based on the best currently available evidence, which is all too often unreliable or insufficient.
Richard Feynman said it best: “I can live with doubt and uncertainty and not knowing. I have approximate answers and possible beliefs and different degrees of certainty about different things. … It doesn’t frighten me.”
We must not be frightened by uncertainty. It is inescapable. We must learn to live with it, especially in medicine.
Mark Crislip said the three words in medicine that are the most dangerous are “in my experience.” I think the three words in medicine that are the most certain but the hardest to say are “I don’t know.”
As Feynman noted, there are degrees of certainty. Doctors are not ivory tower philosophers or scientists. They have to act. They deal in practical applications of science and try to choose the least uncertain options. Their educated guesses can be very accurate. They developed safe and effective COVID-19 vaccines in record time. They changed HIV/AIDS from a death sentence to a chronic disease that is treatable and doesn’t significantly reduce life expectancy. They treat diabetes effectively with diet, drugs, and insulin to reduce the number of deaths and complications. They can’t explain everything or treat everything effectively, but they save lives.
Real medicine may be full of uncertainty, but if it is grounded in reality. It works. Contrast reality-based medicine with the other kind. The other kind (we might call it belief-based medicine) never admits to any uncertainty. It deals in bogus certainties. You will never hear a practitioner of so-called alternative medicine express any uncertainty or doubt. Chiropractors are certain their patients have subluxations. They blithely ignore the fact that different chiropractors find subluxations in different places. And they are happy to disregard the 2009 study by chiropractors themselves that concluded that there is no supportive evidence for the subluxation construct and that subluxation has no valid clinical applicability. Homeopaths are certain the water in their dilute remedies can remember an original ingredient that is no longer there, and they are certain that homeopathy works. If it doesn’t, they find an excuse to blame the patient (for not following directions precisely or for doing something that supposedly interfered with it working). Acupuncturists are certain they can accurately locate meridians and acupoints despite evidence to the contrary, and they truly believe sticking needles in those points somehow magically relieves symptoms and improves health. Nurses who practice therapeutic touch are certain they are manipulating the human energy field despite evidence that they can’t detect that imaginary field when their view of the patient is obstructed. All of these practitioners fail to realize that their patients may just be responding to attention, relaxation, and the provider’s confidence—and they may be experiencing a placebo response.
We all crave certainty. Perhaps that’s why so many people are inclined to listen to cocksure quacks who claim to know the one true cause of all disease rather than to real doctors who are honest enough to say they don’t know what is wrong. Uncertainty is a fact of life, and we must learn to accept it and deal with it appropriately.
This article was originally published as a SkepDoc’s Corner column in Skeptical Inquirer.