Do Quantum Properties Describe Reality?

In my philosophy of science class we have been discussing whether or not scientific or mathematical ideas related to actual reality. It is an interesting question. When people are asked what defines science, they will usually agree that science is the attempt to describe the natural world. Although this seems simple, the branch of physics called quantum mechanics throws simple definitions into disarray. Quantum mechanics deals with the unobservable parts of nature: the subatomic particles that make up the world that is experienced but are impossible to directly view. Since its inception, this field has caused deep philosophical questions for scientists. If a researcher is discussing the properties of a subatomic particle like an electron are scientists to believe that the researcher is describing a piece of reality?

Two schools of thought have emerged because of this conundrum. One, the realists, believe that when scientists are discussing the unobservable world their claims should be taken as describing real particles with real properties. On the other hand the instrumentalists believe that the particles that are discussed are convenient fictions that scientists have created to describe interactions and outcomes that are otherwise impossible to comprehend. For an instrumentalist an electron, for example, does not exist as a physicist would describe it, but rather that it is just a placeholder idea for a negatively charged something that obeys the Pauli exclusion principle. These two ideas are interesting, but present a false dichotomy. It is not necessary to choose one or the other. Indeed, modern philosophers of science have proposed that other options do exist and should be considered. Most compelling among these ideas is cognitive instrumentalism.

For a cognitive instrumentalist describing unobservable objects is faulty but not false. Take an electron for example. Certainly there is something that exists which scientists have named the electron. Studies of this subatomic particle are fundamental to modern science and have created the modern electronic world. Stating that an electron is just a convenient fiction is wrong because researchers have used them to create the modern world. But what about the properties of an electron? It is clear electrons have mass and a charge. However, considering the spin of an electron causes problems. Electrons are said to have a spin of ½ meaning that they must rotate twice to return to their original configuration. This seems absurd and goes against conventional wisdom, yet the spin quantity is critical in Fermi-Dirac statistics. What must be assumed is that the spin quantity does not actually describe a spinning electron, but rather is convenient nomenclature that is used to describe the relationships between electrons. The electron is real, but that specific property is just a convenient fiction. This is the stance of a cognitive instrumentalist.


A leading argument against this stance is the “no miracles” argument. For a strict realist, it seems unlikely that convenient nomenclature would actually be able to make any sort of predictions. If researchers are not describing something that actually exists (in this case electron spin) then researchers are very lucky that it actually worked.

On the other hand, a strict instrumentalist could claim that quantum reality is so beyond experience that it is problematic to judge whether a quality is real or not based on a limited macroscopic world view. In the macroscopic world objects only have to spin 360 degrees to return to their original state, but who is to say that those rules apply at the microscopic level? A scientist can never know, and thus can not make statements about the characteristic of an electron or whether it actually exists.

However, both of these sides are wrong, though the instrumentalist is more correct. For quantities like the spin of an electron, a realist may have an easier time arguing in favor of their position because an electron can conceivably be actually spinning. But when the realist line of reasoning is extended to all subatomic properties contradictions arise. One example will suffice. When describing the interactions between quarks and gluons, physicists assign them each a “color charge” to describe how they interact. There are three color charges (not counting their anti-charge): red, green and blue. If the realist is right, scientists are expected to be believe that a quark is literally one of those three colors. This is absurd. Obviously researchers are not actually describing the color of a quark, it is just a convenient fiction that describes their interactions. The name is a mere semantic trick, an agreed upon nomenclature so that scientists can discuss quarks easily. Thus by this counter-example it is obvious that there are properties that do not describe what their name implies. Rather, they are fictions invented for convenience and the realist point of view has no foundation.

The instrumentalist viewpoint must also be questioned. Certainly an electron does exist because the influence of an electron can be observed and worked with. Ignoring the reality of an electron ignores a large part of scientific thought. Considering this, it is obvious that the cognitive instrumentalist viewpoint is the most sound. Subatomic particles exist as they are described, but the properties that they are assigned may not actually corresponding to their macroscopic counterparts.


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