How chemistry defies
philosophy of science

Published December 01 2016

Hypothesis generation and falsification lie at the heart of the scientific method. Whether it’s investigating the forces governing the motion of planets or galaxies, testing factors influencing the feeding behavior of birds, or constructing molecular models of drugs interacting with proteins, hypothesis testing and falsification are such a ubiquitous part of scientific research that many scientists take them for granted. When you look at the larger landscape of science, however, a more complex view of applying the scientific method emerges, one in which doing science does not depend only on constructing or falsifying specific hypotheses. In fact, non-hypothesis-driven science has been an integral part of scientific progress for a very long time. This fact is exemplified best by the science and art of chemistry.

At first sight, the lack of hypo-thesis-driven science poses a conundrum. If you don’t have a hypothesis, how would you know what experiment to perform or what quantity to calculate? Yet when chemists synthesize new molecules, they seldom have a hypothesis in mind. The hypothesis may lie in the application of those molecules; for example, one may be making a molecule to test a hypothesis about the workings of a particular biochemical pathway or about the quantum yield of a particular solar cell. But the synthesis itself is not really in the domain of hypothesis testing. The oft-quoted comparison between chemistry and architecture thus is not without merit from this viewpoint: When you are laying down plans for a new bridge, what hypothesis exactly are you generating?

The same goes for another pillar of science — namely, falsification. When a chemist is synthesizing a new molecule, she is not expressly trying to falsify a hypothesis except in the trivial sense of trying to falsify the basic laws of chemistry. As the chemist and Nobel laureate Roald Hoffmann of Cornell University elegantly put it in an essay collection called “Roald Hoffmann on the Philosophy, Art, and Science of Chemistry”:

“What theories are being tested (or falsified, for that matter) in a beautiful paper on synthesis? None, really, except that such and such a molecule can be constructed. The theory building in that is about as informative as the statement that an Archie Ammons poem tests a theory that the English language can be used to construct novel and perceptive insights into the way the world and our minds interact. The power of that tiny poem, the cleverness of the molecular surgery that a synthetic chemist performs in creating a molecule, just sashay around any analytical theory-testing.”

Chemistry is largely a creative activity, trying to come up with novel ways of deciphering the structure of molecules and of making them. Synthesis always has been the unique element at the heart of chemistry. Chemists synthesizing molecules are like termites building an intricate nest; the humans who make molecules are no more trying to falsify molecule building than termites are trying to falsify termite-mound building. The goal is to create novelty, not to falsify existing ideas.

This principle applies to a wide range of fields in chemistry. For instance, consider two pillars of tool-driven revolutions in biochemistry: X-ray crystallography and nuclear magnetic resonance spectroscopy. The goal of both techniques is to determine the structure of complex molecules like proteins. Sometimes the goal may be to test specific hypotheses regarding the function of these molecules, but equally often it’s simply to figure out their structures for their own sake. Today there are literally hundreds of thousands of proteins whose structures have been determined, but structure determination by itself is as much art as science. It’s simply being driven by the pleasure of finding things out.

Sometimes the goal is also esthetic. Cartoon models of proteins adorn biochemistry textbooks in the manner of paintings adorning national galleries. Their contours and three-dimensional structures are as much works of visual pleasure as examples of hypothesis testing. The same goes for the study of countless biochemical and genetic pathways in living organisms. Scientists who perform this painstaking detective work are not always testing or falsifying hypotheses; they simply are trying to find out unique biochemical features of living systems.

The fact that much of chemistry and biochemistry defy both hypothesis testing and falsification highlights the limitations of the traditional philosophy of science as it’s currently taught. One of the reasons this is so is that the philosophy of science traditionally has been created, taught and proselytized by people with a background in physics. Many of the big names in the philosophy of science — Aristotle, David Hume, Karl Popper and Thomas Kuhn, to name some of the most prominent — were trained in physics, thought mostly about physics, lived during a time of great upheavals in physics or were influenced by physicists. Kuhn and Popper especially came of age in the heyday of physics. Kuhn, who was a physicist himself, had written extensively about the Copernican revolution and other topics in physics and astronomy before he published his seminal work “The Structure of Scientific Revolutions.”

The principles laid out by these philosophers of science were not incorrect. But they illuminated only one aspect of scientists’ daily work, and incompletely at that. For example, falsification is almost never on the minds of everyday scientists working on their everyday problems. What’s on their minds is confirmation. Neither do most scientists throw away their theories when a few experiments threaten to falsify them; if they did this every time, the progress of science would be much slower than it is.

Even in physics, there are now subfields like the physics of emergent systems in which hypothesis generation and falsification are not the most important activities. Isaac Newton was not wedded to hypotheses. In one passage of his famed “Principia,” he remarked, “Hypotheses, whether metaphysical or physical, or based on occult qualities, or mechanical, have no place in experimental philosophy.”

The problem with much of philosophy of science, then, is not that it’s invalid; it’s that it’s biased by the backgrounds of the philosophers who preach it and the existing fashions of the time. As Hoffmann says, the philosophy of science might have looked very different if it had been taught by chemists, emphasizing synthesis and exploration instead of hypothesis generation and falsification. 

Every science shares some facets of the traditional philosophy of science, but it also has its own explanatory devices that render its philosophy unique. Chemistry is a model example of why as science changes its philosophy must change and adapt, retaining the most cogent of the old principles but nimbly incorporating new ones.

Ashutosh Jogalekar Ashutosh Jogalekar is a chemist doing research in biotechnology and is passionate about the history and philosophy of science. Follow him on Twitter. An earlier version of this article appeared on Jan. 8 on the blog The Curious Wavefunction.