What makes a dog a dog and not a cat?
Essentialism is the belief that familiar categories — dogs and cats, space and time, emotions and thoughts — each have an underlying essence that makes them what they are. The belief in these essences, and the search for them in nature, is a giant misdirection that hampers scientific progress. It’s also a key concept in my new book, How Emotions are Made: The Secret Life of the Brain.
Before Darwin, scholars believed each species had an underlying essence, and variation was considered error. A dog was a dog because it had a “dog essence” that other animals didn’t. Darwin challenged this essentialist view, observing that a species is a population of varied individuals, not erroneous variations on one ideal individual.
Even as Darwin’s ideas became accepted, essentialism held fast. Soon, biologists declared that a new essence, the gene, fully accounted for Darwin’s variation. Nowadays, however, we know that different combinations of genes produce the same characteristics (a.k.a., degeneracy), and that gene expression is regulated by the environment. These two discoveries, after much debate, prompted a paradigm shift in biology. Essentialism lost again.
In physics, before Einstein, scientists thought of space and time as separate physical quantities. Einstein refuted that distinction, unifying space and time and showing that they are relative to the perceiver. Even so, essentialist thinking is still on display when someone asks, “If the universe is expanding, what is it expanding into?”
In my own fields of psychology and neuroscience, essentialism is still widespread. A well-known example is the search for areas in the human brain that are dedicated to each emotion. Originally, scientists assumed that each emotion lived in a specific brain region (e.g., that fear occurs in the amygdala). There’s now plenty of evidence, however, that each so-called “emotional” brain region increases its activity for many mental functions. The amygdala is not just engaged during fear or even emotion, and sometimes not even in fear.
Some scientists today continue to search for the fabled brain essence of each emotion in a single, dedicated brain network, or in a single, probabilistic pattern across the brain, always assuming that each emotion has an essence to be found. Fortunately, an increasing number of scientists are abandoning essentialism as Darwin and Einstein did.
Ridding science of essentialism is easier said than done. Consider the simplicity of this essentialist statement from the past:
“Gene X causes depression.”
It sounds plausible and takes little effort to understand. Compare this to a more recent explanation:
“A given individual in a given situation, who experiences that situation as stressful, will have a change in the sympathetic nervous system that encourages certain genes to be expressed, making him vulnerable to depression.”
The second explanation is more biologically realistic but way more complicated. No wonder essentialism is so enticing. But most natural phenomena do not have a single root cause. The world is a complex place.
This discussion is more than a bunch of metaphysical musings. It affects your life in areas as diverse as national security, the legal system, treatment of mental illness, and the toxic effects of stress on physical illness. I discuss all these topics (and make sense of the real-world complexity behind them) in How Emotions are Made: The Secret Life of the Brain.
[A variation of this post was originally published on edge.org.]