I could have called this post “The war between science and philosophy” or “the zero sum game” but I found it too childish to tackle a subject which is important for the future of physics. There was a recent update in the “discussion” of the role of philosophy in science. Massimo Pugliucci, Sabine Hossenfelder, to take the most recent insightful articles, took position on the claim that “philosophy is not useful to do physics”. As a baseline physicist (i.e. not one working on the fundamental questions of the universe), I have to react and say why I need philosophy. First, please excuse in advance my lack of clarity and of accuracy: I do not have the experience and talent of most participants to this debate. Yet I hope to convey enough of my message to make it useful.
I would first like to cut short one objection : that I am not a theoretical physicist working on “advanced subjects” like string theories, quantum loop gravity and thus I am not entitled to discuss this kind of fundamental issues. Indeed, I am a plasma physicist; I try to understand the phenomena occurring in a plasma, how it is produced, how it reacts to some stimuli. The most “advanced” tool that I use is Quantum Field Theory to calculate some in the measurement of the plasma electric field in a magnetized plasma through Stark effect. Beyond that, I follow what happens in theoretical physics (I do not like this term because it implies a fundamental separation between experiment and theory) and I enjoy what I am able to grasp of the beauty of the constructions (as I enjoy the glimpse at the category theory or at the harmonic forms) but I have no practical experience there. Yet, I think that the reflection occurring at the level of theoretical physics affects the whole physics, whatever the domain, otherwise it would be a strong, if not deadly, blow at its coherence.
To address now the core of my ideas: as a physicist, philosophy is useful for me at two levels: first, at a practical level, because I am an human and not a pure rational machine and it is sometimes difficult to bridge the gap between the human part and the physicist part. Second, at a theoretical level, because the goal of a physicist, more generally of a scientist, is to understand the world as a whole and, unfortunately science fails at some point. Let’s examine these two points in more detail.
The job as a physicist is to apply the scientific method, which is characterized in the daily life by two characteristics: rationality and falsifiability. You take some assumptions, you derive a model from them and experimental predictions from the model, you do some tests and check if you validate or not the model. If not, you check that your chain of thoughts is rational and if it is, you change the assumption. So, basically, from the assumptions to the test/theory comparison, it is basically algorithms (sorting, pattern matching, tree traversing) in actions , except that for the moment only human brains can deal with the fuzziness of reality and the absence of clear-cut borders to the area of investigation, you can always find new ramifications to other topics and you have to expand your analysis. But computers are progressing fast and taking over a big part of this work.
But what about the assumptions, where are they coming from? By deriving them from other assumptions. Good, you see the problem. So, there is always a moment (or even several) in the day of the physicist, when all scientific methods are exhausted, where he scratches his head with a sigh. What is the practical solution there? he takes height: he tries to establish analogies with other problems, he conceives random or impossible assumptions, he drinks a coffee or goes to the theatre until the inspiration comes back. But the most effective solution is to go to the office of his colleague and discuss. And when the problem is serious (i.e. all scientific ways are exhausted), the discussion is of philosophical nature (even if not with the quality of experienced philosophers): he tries with his colleague to elaborate concepts with words. Who said that words were not accurate enough to do science? They are not as accurate as equations, but their fuzzy nature is of a lot of help when your mind is trapped by the rigidity of the equations. They give you the room to expand the mind and to discuss with your colleagues. How many scientists discuss only with equations? This is not for nothing that it is asked to reduce the number of equations in a presentation: they are a bad tool for discussion and presentations are an invitation to discussion. The philosophical discussion reduces the accuracy of the ideas but gives more flexibility and opens new areas. In this sense it is complementary of the scientific method. By the discussion (with yourself or with your colleagues) you explore new ideas and you establish new assumptions. When you come to an agreement, you apply the scientific method to them and the machine is running again.
This is also where you understand that experimental results are very useful, not only to validate or invalidate a theory, but to discuss: they are as fuzzy, or even fuzzier, as words: the experimental between two experimental sets of data will never be perfectly linear, you will have some scattering which will invite to discussion: is it really linear? Should we add a bit of non-linearity to the interpretation? New ideas often happen from the discussion of experimental results.
This is why the scientists should be more trained to the philosophical method: this would improve their discussions and give the tools to elaborate concepts more easily before transforming them in scientific models. It will also probably improve the quality of the human relations and remind them that they are not purely rational machines (and maybe prevent some nervous breakdowns).
The second level of interest for philosophy is more fundamental. There is a point where the scientific method does not work when you try to understand the world when you live. Actually, it breaks for most of the daily issues (except if you live in a lab or your name’s Sheldon): your relations with the society, politics or your love affair. You can write a numerical model of your relation and test it. If the test fails, it will not be possible to change the model! Facing this situation, either you just live your life or, if you really want to understand, philosophy is the only possible rational way to approach the problem. This is only what you can do when you meet the absurd, as defined by Albert Camus in the Myth of Sisyphus: the absurd arises when the human need to understand meets the unreasonableness of the world, when “my appetite for the absolute and for unity” meets “the impossibility of reducing this world to a rational and reasonable principle.”. The worst moment for a scientist.
Of course, you can say that, in the end, physics will explain everything (we could discuss that, personally I am not convinced, not with the present tools), we are just limited for the moment by our ignorance. Sure but now is the moment where we live and if we want to avoid too much frustration, we have to use all possible rational tools to quench our thirst of knowledge or, for the least, to deal with the world.