Some Notes on the Nature of Science

Joe Schwarcz, Ph.D.
Stephen Barrett, M.D.

The scientific method offers an objective way to evaluate information to determine what is false. The late astronomer Carl Sagan, Ph.D., has pointed out that "Science is a way of thinking much more than it is a body of facts." [1]

A 1998 National Academy of Sciences book contains a superb chapter that distinguishes between facts and theories and between scientific beliefs and faith [2]. Although the book focuses on evolution, its reasoning is equally applicable to health-related issues. The book states:

In scientific terms, "theory" does not mean "guess" or "hunch" as it does in everyday usage. Scientific theories are explanations of natural phenomena built up logically from testable observations and hypotheses. . . .

Scientists most often use the word "fact" to describe an observation. But scientists can also use "fact" to mean something that has been tested or observed so many times that there is no longer a compelling reason to keep testing or looking for examples. . . .

Usually "faith" refers to beliefs that are accepted without empirical [observed] evidence. Most religions have tenets of faith. Science differs from religion because it is the nature of science to test and retest explanations against the natural world. Thus, scientific explanations are likely to be built on and modified with new information and new ways of looking at old information. This is quite different from most religious beliefs.

Therefore, "belief" is really not an appropriate term to use in science, because testing is such an important part of this way of knowing. If there is a component of faith to science, it is the assumption that the universe operates according to regularities. . . . This "faith" is very different from religious faith.

The following ideas can help you evaluate information you encounter about science and health.

  1. Science is a truth-seeking process. It is not a collection of unassailable "truths." It is, however, a self -correcting discipline. Such corrections may take a long time—the medical practice of bloodletting went on for centuries before its futility was realized—but as scientific knowledge accumulates, the chance of making substantial errors decreases.
  2. Certainty is elusive in science, and it is often hard to give categorical "Yes" or "No" answers to scientific questions. To determine whether bottled water is preferable to tap water, for example, one would have to design a lifelong study of two large groups of people whose lifestyles were similar in all respects except for the type of water they consumed. This is virtually impossible. We therefore have to rely on less-direct evidence in formulating many of our conclusions.
  3. It may not be possible to predict all consequences of an action, no matter how much advance research has been done. When chlorofluorocarbons (CFCs) were introduced as refrigerants, no one could have predicted that 30 years later they would have an impact on the ozone layer. If something undesirable happens, it is not necessarily because someone has been negligent.
  4. Any new finding should be examined with skepticism. Healthy skepticism does not mean unwillingness to believe. Skeptics base their beliefs on scientific proof and do not swallow information uncritically.
  5. No major lifestyle change should be based on any one study. Results should be independently confirmed by others. Keep in mind that science does not proceed by "miracle breakthroughs" or "giant leaps." It plods along, taking many small steps, slowly building towards a consensus.
  6. Studies have to be carefully interpreted by experts in the field. An association of two variables does not necessarily imply cause and effect. As an extreme example, consider the strong association between breast cancer and the wearing of skirts. Obviously, wearing skirts does not cause the disease. Scientists, however, sometimes show an amazing aptitude for coming up with inappropriate rationalizations for their pet theories.
  7. Repeating a false notion does not make it true. Many people are convinced that sugar causes hyperactivity in children—not because they have examined studies to this effect but because they have heard that it is so. In fact, a slate of studies has demonstrated that, if anything, sugar has a calming effect on children.
  8. Nonsensical lingo can sound very scientific. An ad for a type of algae states that "the molecular structure of chlorophyll is almost the same as that of hemoglobin, which is responsible for carrying oxygen throughout the body. Oxygen is the prime nutrient and chlorophyll is the central molecule for increasing oxygen available to your system." This is nonsense. Chlorophyll does not transport oxygen in the blood.
  9. There often are legitimate opposing views on scientific issues. But it is incorrect to conclude that science cannot be trusted because for every study there is all equal and opposite study. It is always important to take into account who carried out a given study, how well it was designed, and whether anyone stands to gain financially from the results. Be mindful of who the "they" is in "they say that . . . ." In many cases, what they say" is only gossip, inaccurately reported.
  10. Animal studies are not necessarily relevant to humans, although they may provide much valuable information. Penicillin, for example, is safe for humans but toxic for guinea pigs. Rats do not require vitamin C as a dietary nutrient but humans do. Feeding high doses of a suspected toxin to test animals for short periods of time may not accurately reflect the effect on humans exposed to tiny doses over long periods of time.
  11. Whether a substance is a poison or a remedy depends on the dosage. It makes no sense to talk about the effects of certain substances on the body without talking about amounts. Licking an aspirin tablet will do nothing for a headache, but swallowing two tablets will make the headache go away. Swallowing a whole bottle of pills will make the patient go away.
  12. "Chemical" is not a dirty word. Chemicals are the building blocks of our world. They are neither good nor bad. Nitroglycerin can alleviate the pain of angina or blow up a building. The choice is ours. Furthermore, there is no relation between the risk posed by a substance and the complexity of its name. "Dihydrogen monoxide" is just water.
  13. Nature is not benign. The deadliest toxins known, such as ricin from castor beans or botulin from the Clostridium botulinum bacterium, are perfectly natural. "Natural" does not equal "safe," and "synthetic" does not equal "dangerous." The properties of any substance are determined by its molecular structure, not by whether it was synthesized by a chemist in a lab or by nature in a plant.
  14. Perceived risks are often different from real risks. Food poisoning from microbial contamination is a far greater health risk than trace pesticide residues oil fruits and vegetables.
  15. The human body is incredibly complex. Our health is determined by many variables, which include genetics, our diet, our mother's diet during pregnancy, stress, level of exercise, exposure to microbes, exposure to occupational hazards, and pure luck.
  16. While diet clearly plays a role in the promotion of good health, the effectiveness of specific foods or nutrients in the treatment of diseases is usually overstated. Individual foods are not good or bad, although overall diet may be described as such. The wider the variety of foods consumed, the smaller the chance that important nutrients will be lacking. There is universal agreement among scientists that a high consumption of fruits and vegetables is beneficial.
  17. About 80% of illnesses are self-limiting and will resolve in response to almost any kind of treatment. Often, a remedy will receive undeserved credit. Anecdotal evidence is unreliable, because positive results are much more likely to be reported than negative ones.
  18. There is no goose that lays golden eggs. In other words, if something sounds too good to be true, it probably is. As H.L. Mencken once said, "Every complex problem has a solution that is simple, direct, plausible, and wrong."


  1. Sagan C. The fine art of baloney detection. Parade Magazine, p 12­13, Feb 1, 1987.
  2. National Academy of Sciences Working Group on Teaching Evolution. Teaching about Evolution and the Nature of Science. Washington, DC: National Academy Press, 1998.

Dr. Schwarcz is director of McGill University's Office for Chemistry and Society. In addition to teaching chemistry at McGill, he hosts a weekly "phone-in" show about chemistry on Montreal radio station CJAD, writes a weekly column called "The Right Chemistry" in the Montreal Gazette, and has a regular TV feature entitled "Joe's Chemistry Set" on the Canadian Discovery Channel. The above list of 18 tips was adapted from a section of his book Radar, Hula Hoops and Playful Pigs, a collection of commentaries on the fascinating chemistry of everyday life.

This article was revised on June 22, 2001.

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