Karl Popper and Thomas Kuhn’s philosophy of science is rooted in physics, but given the rapid development and heterogeneous nature of the life sciences, it is important to consider whether existing philosophical theories of science can be applied to biology, or whether a new philosophical perspective is needed.
Karl Popper and Thomas Kuhn are two of the founders of philosophy of science as a discipline. They had very different views on the nature of science, but as contemporaries of the 20th century, they both made significant contributions to the establishment of philosophy of science as an academic discipline. What’s interesting about their discussions is that, despite their vastly different views of science, they both grounded their arguments in the physical sciences. This makes sense when you consider their academic upbringings. Popper was born in 1902 and grew up during the formative years of relativity and quantum mechanics, while Thomas Kuhn was a theoretical physicist who became a philosopher of science when he discovered the history of science while preparing for his PhD. It’s no wonder that both men centered their arguments on physics. In the introduction to the fourth edition of Kuhn’s classic work, The Structure of Scientific Revolutions, philosopher of science Ian Hacking makes this point with a reference to Popper.
He also makes another important point: referring to the advent of biotechnology and the 150th anniversary of The Origin of Species in 2009, he says that we should ask ourselves whether Kuhn’s theory applies to the life sciences, since “the life sciences have pushed physics out of the way and taken the top spot in science.” While his statement may sound a bit exaggerated, it’s true that biology has developed rapidly in the second half of the 20th century, and its importance in science has grown dramatically, so it’s worthwhile to consider whether existing philosophical theories of science can be applied to biology.
However, there is one challenge to this task. This is that biology is made up of two very disparate fields. Thinking back to Hacking’s reference, obviously biotechnology and evolutionary theory fall under biology, but there is a clear gap between the two. To give a more real-life example, while we can watch TV documentaries and learn about the ecology of various organisms, the first part of most biology textbooks in college is devoted to chemistry and the behavior of biomolecules. Both are about living things, but the focus is very different.
In his book review of Drosophila – The Hidden Hero Who Changed the History of Biology and Genetics, Ottawa University professor Woojae Kim, a fruit fly geneticist, explains this difference as the existence of two traditions within biology. The tradition of taxonomy or natural history has given way to evolutionary behavioral biology or evolutionary ecology, and the tradition of physiology has given way to molecular biology along with the tradition of physics and chemistry. In The Fruit Fly, Martin Brooks divides modern biologists into two groups: the reclusive and the outdoorsy. The hermits, in the tradition of experimental biologists, work indoors and get migraines when out in the sun. They are represented by biochemists, molecular biologists, geneticists, and biologists who create mathematical models. The outdoorsy types, on the other hand, are lab-averse and include ecologists.
The problem is that the nature of these two fields is so different that it’s not easy to encompass both philosophical accounts of science. For example, evolutionary biology might be better explained by Kuhn’s philosophy of science than Popper’s. Evolution is difficult to verify experimentally because the time span over which evolution occurs is longer than the human lifespan, and although it has undergone many revisions since it was first proposed, it remains the theory that explains many phenomena in the biological world, and there is no competing paradigm. Evolutionary theory takes the form of Kuhn’s normal science, and while it’s not a dramatic scientific revolution, it’s not without its paradigm shifts. Various theories have been proposed about the mechanisms of evolution since Darwin, and the modern synthesis is the current orthodoxy of evolutionary theory. While this doesn’t perfectly fit Kuhn’s theory of scientific revolution, it can be seen as a similar case to Newtonian mechanics still being valued.
Molecular biology, on the other hand, is a field in which Popper’s type of disproving is active. For example, Crick’s Central Dogma of molecular biology was disproved by a virus with RNA as its genome. In molecular biology, verification and disproval are relatively easier than in evolutionary biology because research is conducted in the laboratory using physics and chemistry. However, molecular biology does not have a single paradigm like Newtonian mechanics or relativity. Since the Central Dogma was disproved, a new paradigm that encompasses it has yet to emerge.
What should we make of phenomena that defy a unified view of the two disciplines? It’s important to keep in mind that the two disciplines are complementary rather than antagonistic. Ultimate causation and proximate causation are a good example of this. For example, if you think about why a moth flies toward a light, the answer is that it is because it is advantageous to its survival, which is an ultimate causal explanation, and the answer is that it flies toward the light because of nerve impulses from its light receptors, which is a proximate causal explanation. These two concepts are complementary, not oppositional, and we can say that evolutionary biology is the ultimate causal explanation and molecular biology is the proximate causal explanation.
In this way, it is difficult to explain the nature of biology using existing philosophical theories of science. While physics has not changed much in the way it develops its theories, biology is composed of two different fields, which require different perspectives depending on the nature of the field, or new perspectives that can encompass both fields. For example, new perspectives could be drawn from findings in statistical physics or the physics of complex systems. The point is that it is not enough to simply apply existing philosophies of science.
Let me conclude this article with a thought from the philosopher of science FireAvent, who argued that great scientists were not bound to a particular methodology, and that science is only scientific when it allows a wide variety of hypotheses to be presented without constraint. This is strikingly similar to the conclusions about the philosophy of science in biology discussed in this article. The philosophy of science in biology needs to be presented in a diverse way, and any attempt to reify it with only the existing debates would be to stifle imagination and creativity, and to regress the human intellect.
