Occam's Razor is a widely valued principle in science and beyond. But as the exceeding complexity of our world becomes increasingly apparent, is it time to give up on the virtue of simplicity when it comes to understanding the universe, asks Angela Potochnik.

Simple explanations are widely valued. Occam’s Razor, named for a medieval philosopher, urges us to adopt the simplest theory the evidence allows. Customarily, this is understood as the idea that simple theories are more likely to be true. This idea has been widely influential, and perhaps especially so in science. 

But here’s the problem. It’s increasingly clear that the world we inhabit is exceedingly complicated. Germs cause disease, but it turns out that exposure to germs isn’t the only relevant factor to whether you get sick, and so-called “lifestyle diseases” such as heart disease and strokes aren’t caused by germs at all. 

In 2003 the Human Genome Project completed a full account of human genes, but it has been hitting home since then that human genes are tremendously variable and the influence of individual genes frustratingly difficult to identify. The former observation spurred the 1000 Genome Project, while the latter is such a serious problem it has been named: missing heritability. Scientists now also appreciate that humans are significantly influenced by the genes of the bacteria we host, which outnumber our own cells. Getting to the bottom of this influence is the aim of the Human Microbiome Project. Your health is also influenced by your mother’s and grandmother’s lived experiences, including their stress levels: this is one element of what’s called epigenetics. 

Even physics isn’t immune to all of this complexity. Most work in physics focuses on only the simplest systems, but the physical world is just as complex as living organisms. Just think of all the considerations that influence where a dollar bill lands when you let go of it in the wind on a busy street: not just gravity, but also wind conditions, temperature gradient, building placement, the speed and frequency of vehicles driving by, and so on. 

Our world is defined not by simplicity but by complexity. 

If simple explanations aren’t more likely to be true, why do we seek them? I suggest it’s because of the cognitive value—the “aha!” moment—we experience from grasping a simple explanation. The feeling of having gotten to the bottom of something, to have figured out a clear answer. 

We are willing to compromise some accuracy in order to achieve such simple answers. Some cognitive psychology research suggests that people value general explanations, explanations that feature broad patterns. What is more, it seems people tend to overgeneralize—to take broad patterns too seriously and to ignore exceptions to the patterns. There is a basic mismatch between this craving for simple explanations and the complicated world around us. Simple explanations are not more likely to be true—they are usually more likely to leave out important considerations. 

The cognitive value of simple explanations thus seems to be best understood as a focus on how one or a few salient factors influence a complex phenomenon. This is both enlightening and also an effective guide to exerting control over the world around us. 

"This mismatch between the complicated world we live in and our yearning for simple explanations is accommodated with the judicious use of idealizations"