Are Scientists Objective and Rational? A Review of “The Structure of Scientific Revolutions” by Thomas S. Kuhn

We think of science as a rational, empirical alternative to religion and spirituality. The scientific method is a common denominator for all the different fields in science. Science is the basis for technology, which has improved the standard of living for billions of people. In the developed world, we pride ourselves on public policy being guided by science rather than superstition or tradition.

While science is objective and rational, what about scientists? Are scientists a bunch of supermen not subject to desires, wishes, and prejudices that non-scientists experience? Or are they human beings, with the same frailties and failings that other humans have? Thomas S. Kuhn takes up this question in his almost 50-year-old classic book The Structure of Scientific Revolutions. The question is still relevant today, as science impacts the daily lives of more people in the world than it ever has before.

The question I ask in the title to this review can be rephrased as: Is scientific advancement always linear and progressing at a constant rate, or is it characterized by long fallow periods interrupted by occasional revolutions? The media and textbooks favor the former interpretation. Almost every day, the media reports on some new study or experiment that adds to our scientific knowledge. Science textbooks give students the sense that past historical controversies are irrelevant, and they should focus on solving problems. Past controversies and changes in beliefs are usually only studied by science historians.

Kuhn sees the linear model of scientific advancement as flawed. It doesn’t reflect the reality of science history. Science history, like art, political/economic, technology, and religious history, is characterized by occasional bursts of radical change (i.e. revolutions) surrounded by long periods of stability. Unlike these other fields, however, which all past civilizations possessed in some form, science is much newer and for over four centuries monopolized by Europeans.

Kuhn gives a detailed account of how scientific revolutions happen. To understand revolutions, you need to first understand “normal science,” which is what Kuhn describes as everyday science. Normal science is what most scientists do most of the time. It consists of puzzle solving, of determination of significant fact, of matching facts with theory, and articulation of theory. Examples include determining structural formulas, specific gravities, the speed of light, and arriving at quantitative laws. Normal science is guided by “paradigms,” constellations of beliefs, values, and techniques that are shared by members of a scientific community. A paradigm accepted by all members of a scientific discipline is a prerequisite for normal scientific work. Fundamental disagreements are characteristics of early stages of scientific development, which go away with the adoption of a shared paradigm. An example is the field of optics before and after Isaac Newton. Before Newton, “though the field’s practitioners were scientists, the net result of their activity was something less than science” (p. 13). Because there was no shared paradigm, everyone writing on optics had to articulate the foundations of his viewpoint. After Newton, scientists accepted his theory of light, and normal scientific optical work began.

A contemporary example of a pre-scientific field is clinical psychology. Psychodynamic therapies differ on fundamentals with cognitive, behavioral, family, sociological, and biological therapies. There is no shared paradigm uniting those who practice these different styles of therapies. As a result, clinical psychology has not made the progress characteristic of mature scientific disciplines like biology, chemistry, or physics.

Newton’s particle theory of light was eventually replaced with newer theories. The first theory to replace it was the wave theory, which derived from the optical writings of Young and Fresnel in the early nineteenth century. This was then replaced in the twentieth century with the contemporary theory of light as photons, with some characteristics of waves and some of particles. This theory derived from the work of Planck, Einstein and others. Each of these changes in theory was an example of a scientific revolution, a topic to which Kuhn devotes most of his book.

Scientific revolutions begin with “anomalies”, experimental results that violate a paradigm-induced expectation. Anomalies usually come about as a result of normal scientific work. One famous example is the late-nineteenth century crisis in physics that led to Einstein’s relativity theory. The wave theory of light, which became the paradigm of the nineteenth century, held that there must be a mechanical ether through which light propagated. All other waves traveled through some medium, and light was no exception. Anomalies arose, however, when both celestial observations and terrestrial experiments failed to find any drift of light through the ether. These anomalies provoked a “crisis”, an unstable condition in which a new paradigm has a good chance of acceptance. Einstein’s special theory of relativity, which he published in 1905, was a direct response to this crisis. This theory led to a new physics paradigm not only about the nature of light, but also about relative space, mass, and motion.

The above analysis is compatible with objective and rational scientists. When they practice normal science scientists are objective. After a new paradigm is accepted, and the crisis which led to it is resolved, scientists are objective. It is in their response to anomaly, and their resistance to change during revolutionary periods, that scientists reveal that there are only human.

When anomalies happen, such as the problems verifying an ether medium through which light travels, scientists have a few options:

1) They can stick with the current paradigm, and either ignore the anomalies, or try to come up with theories explaining the anomalies. Many times these theories are competing. Sometimes these theories and revisions of theories create a confusing mess, such as the modifications to Ptolemaic astronomy that occurred during the Middle Ages.

2) They can abandon the current paradigm in favor of a new one. This presupposes that some creative individual or group of people has put forth an alternative.

When a new paradigm is offered to the scientific community, it usually has not been verified, and doesn’t fit the existing facts and observational data better than the old one. For example, Copernicus’ heliocentric theory did not explain existing astronomical data better than Ptolemaic geocentric theory. It took years for Einstein’s theory of relativity to be experimentally verified.

That’s why scientists cannot choose between competing paradigms based on fact or logic. Many times new theories have an esthetic appeal to some scientists. These scientists help promote the new theory, and bring a greater likelihood that experiments or observations will be done to verify the theory.

Most scientists will stick to the current paradigm, even if it has many anomalies. This is due to the fact that they are human, and most humans resist change. This can be seen in nonscientific contexts. Contemporary American political life is characterized by widespread corruption, inefficiencies, and indebtedness. But due to inertia, it’s very hard to enact even the most basic and obvious reforms. From an external, objective perspective, this resistance to change is irrational, just as scientists sticking to flawed paradigms are irrational. But most people will defy logic and reason in order to maintain stability.

There are some scientists who will embrace a new paradigm. These people have different personalities than most—more open to new experience, more novelty seeking, and less bound to tradition. The most extreme examples are scientists who come up with the new paradigmatic theories. They are usually very young or new to the field. Einstein was in his mid-twenties and not yet a professional scientist when he published his paper on the special theory of relativity.

Let me use a current example to illustrate Kuhn’s thesis. I previously mentioned clinical psychology as pre-scientific field, one that has competing paradigms and theories. This is true when one looks at clinical psychology as a whole, including both psychologists and psychiatrists. Let me focus, however, on psychiatry, i.e. medical doctors who specialize in mental health. They have a shared paradigm, the biochemical/drug theory, which states that mental disorders are caused by chemical imbalances that can be treated by drugs. It’s rare to find a psychiatrist who has time or inclination to provide any kind of talk therapy. Most of them are now pill pushers, who restrict patient interaction to brief sessions, primarily to make diagnoses.

This wasn’t always the case. In the middle of the twentieth century, psychiatrists had a much different paradigm, Freudian psychoanalysis. They spent their time in lengthy analytical sessions with patients. When psychiatric drugs were first introduced in the 1950’s, they were a novelty, and most psychiatrists continued doing psychoanalysis. But over the next few decades, psychiatrists eagerly embraced the new biochemical/drug paradigm. It isn’t hard to understand why. Psychiatrists are trained as medical doctors, which means that they have to take the same biology, chemistry, and physics classes that other doctors take. They had extensive knowledge of anatomy, physiology, and biochemistry that was wasted when they became psychoanalysts. By prescribing drugs to treat mental disorders, however, they got to be “real” doctors. They could put their medical knowledge to use in their professional life, something that they couldn’t do when they were psychoanalysts.

Over the next half century, the biochemical/drug paradigm developed anomalies. These anomalies were summarized by Robert Whitaker in his recent book Anatomy of an Epidemic. The chemical imbalance theory, i.e. that schizophrenia is caused by too much dopamine, and depression by too little serotonin, was never verified. Scientists haven’t made much progress in understanding the cause or pathophysiology of mental illness. Diagnosis is still based on symptoms due to a lack of any reliable or valid lab tests. Drugs that seem to help patients in the short term, have a much more problematic long-term outcome. As newer drugs began to be prescribed more frequently, patients seemed to function worse than they ever did before, many of them becoming permanently disabled and unable to work. Corruption became endemic, with many leading psychiatrists becoming paid spokesmen for drug companies.

In spite of these anomalies, most psychiatrists (and biological mental health researchers) continue to support the biochemical/drug paradigm. Part of the reason for this is the normal resistance to change that I described above. Another reason is that there has been no newer biological paradigm for mental illness. According to Kuhn, “a scientific theory is declared invalid only if an alternate candidate is available to takes its place” (p. 77).

There’s no way to predict how long the wait will be for an alternate candidate. In the case of the crisis in physics about the nature of light, a new theory became available within decades. It took over a millennium for an alternative to the geocentric Ptolemaic theory to arise.

The reason why we can’t predict when an alternate paradigm will come forward is that scientific creative achievement is not linear and progressive. As Kuhn describes in his book, scientific progress is characterized by long sterile periods of pre-science or normal science, interrupted by occasional revolutions. Many times these revolutions are the result of individual creative genius, as in the case of Copernicus, Newton, Darwin, and Einstein. Understanding the psychological characteristics of creative individuals, and the social characteristics of societies that promote create achievement, is beyond the scope of this book. For a psychological perspective, I recommend Eysenck’s Genius or Simonton’s Origins of Genius. For a sociological perspective, I recommend Murray’s Human Accomplishment.

The Structure of Scientific Revolutions is only about 200 pages, and not difficult to read. I’m not interested in the philosophy of science, and sections devoted to philosophy I found boring. I’m more interested in historical examples, and found the historical sections more interesting. A problem is that Kuhn briefly goes over some of the older theories and experiments, and I would have preferred to see a more thorough explanation, including illustrations. Another problem is that Kuhn’s examples are exclusively in the physical sciences, and I would have liked to see more biological and psychological examples.

Notwithstanding these limitations, this book is a classic in the history and philosophy of science. I recommend it to anyone interested in science and creativity.