Are Electrons Real?

Henne: Scientific realism is the view that successful scientific theories provide a true picture of the world. So when a theory posits electrons, phonons, and other entities that underlie our observations, the realist takes those to genuinely exist independently of us. Additionally, scientific realism holds that our current theories are unlikely to be completely overturned in the future, although they might get refined, expanded, or subsumed within more general theories. So if an alien civilization were to come up with its own scientific theories, they would share similar entities and structures with ours.

Henne: The opposite of realism is instrumentalism, which says that science is an instrument for describing and predicting phenomena rather than providing a literally true account of the underlying reality. Subscribers to instrumentalism might say that scientific theories don’t even claim to be about what fundamentally exists. Or they might say that, even if these theories do aim to describe the world, we have no way of knowing if they’re true or not. We can only say that they are empirically adequate, that is, they correctly describe and predict what we can observe.

Henne: Some philosophers seek a compromise between realism and instrumentalism. They say that only certain parts of scientific knowledge correspond to reality. One of the two main variants of this view is entity realism, which maintains that science is about real entities like electrons or atoms—objects we can manipulate in experiments. But this school of thought remains agnostic about the truth of the theories telling us what these entities really are. The other is structural realism, which suggests that what is fundamentally real is the mathematical structure captured by our theories, which often survives changes in theory. These philosophers are less convinced of the reality of the entities themselves.

Tomczyk: A realist would usually say that, if a successful theory necessarily includes entities such as electrons or phonons, then those objects are real. That realist would be as committed to the reality of phonons as they are to the reality of electrons. That said, phonons and other quasiparticles are less familiar to us; they don’t feel as “thing-like.” Even if one accepts the arguments of realism, the question remains as to which entities should count as candidates for being real.

Tomczyk: The debate on scientific realism usually centers on the status of unobservable entities—things that cannot be perceived with our unaided senses.

Henne: But philosophers—including realists and instrumentalists—don’t always agree on the boundary between observable and unobservable. Some instrumentalists say that we should remain agnostic about the existence of anything that’s not observable with our unaided eyes, which would include electrons and even microbes. But I think most philosophers view this boundary as a spectrum rather than a sharp divide. So they would be realists about cells, for example, even though we need a microscope to observe them. Usually, the question of existence is for highly theoretical entities that can only be inferred from complex data.

Tomczyk: We created a survey with 30 statements that captured elements of different philosophical views. We then performed a cluster analysis on the basis of the extent to which the respondents agreed or disagreed with the statements and examined correlations between the respondents’ clusters and variables such as their field of physics, experimental or theoretical focus, and seniority.

Henne: I would be in the cluster corresponding to a view known as perspectival realism: Science provides genuine understanding of how the world works but only through partial perspectives on reality. While theories do latch onto real phenomena, we acknowledge that science is very much a human construction.

Tomczyk: I would either belong to the same cluster as Henne or to the instrumentalist one. For me, there’s a question of what realism even means. Classical realism suggests that a good theory is one in which each term corresponds to one entity in reality. I found this view comfortable for a long time. But it relies on the idea that the world itself is already carved into things and properties, independent of our verbal constructs. I don’t agree with that view, so I cannot be a realist in a classical sense.

Tomczyk: I would say yes, electrons are real in the sense that we measure them and we work with them. But if humans did not exist, it’s hard to say what it would even mean for an electron to be real. For us, an electron is partly a mathematical object, and it is something that we investigate in experiments. Without mathematics and experiments, we couldn’t really say what it is. And if you take away the human, you take away both mathematics and experiments. Then there’s not much left.

Tomczyk: It likely won’t affect how they approach a specific project, but it could shape their long-term goals. Do they want to know about the building blocks of the Universe? Then particle physics might be the focus. Do they want new technologies? Then maybe solid-state physics is a better fit.

Henne: Intuitively, we expect physicists with realist tendencies to prefer different fields from those favored by physicists with more instrumentalist tendencies. But we didn’t find any significant correlation between physicists’ views on realism and their preferences for experimental versus theoretical or basic versus applied research. That is surprising because one might expect people working at CERN, for example, to be more realist as they seek to uncover the fundamental building blocks of nature.

Tomczyk: The only correlation we found—and that was weak—is that realist-oriented people tend to value investing money to build a big particle collider to probe the nature of reality, whereas antirealist people are more likely to view such projects as too expensive.

Tomczyk: For Galileo and Newton, philosophy and physics were not separate fields. It would be valuable for contemporary physicists to engage more with the philosophical aspects of their work. I have friends from physics who have mulled these topics a lot, but not in the technical terms of philosophy. And as a philosopher, you can attend a physics conference, but you probably won’t understand much. That’s unfortunate. Both sides have valuable input to contribute, but they don’t often come together.