Pseudoscience, common sense, and the problem of scale

Scientists are increasingly frustrated by laypeople’s willingness to embrace pseudoscience. In an age of extraordinary technical achievement, the persistence of nonsense beliefs like creationism, vaccine rejection, and homeopathy is difficult to fathom. But Scott Lilienfeld, a psychology professor at Emory University, argues that we should be anything but surprised.

Explaining Why Scientists Shouldn’t Be Surprised by the Popularity of Intelligent Design, Lilienfeld asserts:

… [F]rom the standpoint of psychological science, the only thing about [intelligent design’s] popularity that should surprise us is that so many scientists are surprised by it…

It’s just a matter of common sense. No, advocates of pseudoscience aren’t lacking in common sense. The problem is precisely the opposite. They believe that they can use common sense to evaluate scientific claims.

The foremost obstacle standing in the way of the public’s acceptance of evolutionary theory is not a dearth of common sense. Instead, it is the public’s erroneous belief that common sense is a dependable guide to evaluating the natural world…

Yet natural science is replete with hundreds of examples demonstrating that common sense is frequently misleading. The world seems flat rather than round. The sun seems to revolve around Earth rather than vice-versa. Objects in motion seem to slow down on their own accord, when in fact they remain in motion unless opposed by a countervailing force.

Fundamentally, this is a problem of scale. What is common sense? It is a body of knowledge derived from common experience. Even toddlers know that objects always fall down not up and objects that are out of sight still exist. These rudimentary scientific observations form the bedrock of common sense. But for something to be common sense, it must take place on a level we can appreciate with our senses. Simply put, common sense can only tell us about events that are common to human experience.

Yet what we can apprehend with our unaided senses represents only a small fraction of what is going on. Our distance vision is limited. Microscopic organisms and particles are invisible to us. No individual has personal experience of a time span longer than 100 years or so. Therefore, many scientific processes take place at a scale that is impossible for us to perceive. Whether that scale is distance measured in light-years, size measure in microns or time measured in millennia, they are entirely outside the realm of common sense.

… The human brain evolved to increase the probability that the genes of the body it inhabits make their way into subsequent generations. It did not evolve to infer general principles about the operation of the natural world, let alone to understand itself. It also did not evolve to comprehend vast expanses of time, such as the unimaginable tens or hundreds of millions of years over which biological systems evolved. Consequently, it is hardly surprising that many intelligent individuals … glance at the remarkably intricate biological world and conclude that it must have been produced by a designer.

Lilienfeld is referring to the “watchmaker” theory of intelligent design: Imagine walking through a barren desert and finding a functioning watch in the sand. Common sense tells us that such an intricate and complicated object could not have arisen spontaneously. Even though we cannot see a watchmaker, we can infer that a watchmaker must exist.

Yes, that is what common sense tells us, because in our common experience, complex objects do not arise spontaneously. But our common sense draws on what humans have learned during the 10,000 years of recent history. However, evolution takes places on an entirely different scale, over hundreds of thousands of years. No amount of common sense can tell us how it works because it is outside the realm of our common experience.

This is the same reason why it took almost all of human existence until we figured out that the earth is round, not flat. Common sense tells us that the earth is flat because it looks flat when we observe it, and it feels flat when we walk upon it. In other words, it seems flat to us at the scale that we are able to observe with our unaided senses. We cannot see vast distances and we cannot feel minute curvature. Take us to a different vantage point, though, the shape of the earth is easy to appreciate. Looking at the earth from space, it is obvious that it is round.

Common sense tells us that the universe revolves around the earth. That’s the way it looks to us, but, again, that is only because we are restricted by the limitations of the human frame of reference. Once the telescope was invented, and Copernicus and Galileo were able to discern other planets and take precise measurements of what happens in the sky each night, it became apparent that the earth was moving through space rather than space moving around the earth.

Common sense is often useless in evaluating scientific phenomena because they take place outside the scale of common experience. Yet scientists have not appropriately emphasized this fact. According to Lilienfeld:

To a substantial extent, the fault in the current [intelligent design] wars lies not with the general public, but with scientists and science educators themselves. Generations of biology, chemistry, and physics instructors have taught their disciplines largely as collections of disembodied findings and facts. Rarely have they emphasized the importance of the scientific method as an essential toolbox of skills designed to prevent us from fooling ourselves…

… [Scientists] must inculcate in students a profound sense of humility regarding their own perceptions and interpretations of the world. They should teach students about optical illusions, which demonstrate that our perceptions can mislead us…

Believers in pseudoscience do not lack common sense. Rather, they lack an understanding of the limitations of common sense. Anything that takes place at a scale too large, too small, or over a period of time too long to be perceived by unaided human senses is not amenable to understanding through common sense. Common sense is helpful in judging only what we commonly experience. When it comes to phenomena that occur on a scale we are incapable of experiencing, common sense is virtually useless.