How I learned to stop worrying and embrace contextuality
Quantum mechanics is contextual: not all properties of a system are defined at all times. The confusion stems from a common misconception: things are what they are only because of their intrinsic features. A chair is a chair because it is a chair. Unfortunately, things are not that simple. A chair is a chair because we are on the surface of the earth. A chair would not be a chair for long on the surface of the sun. The fact that we have a chair, and not a small amount of plasma, depends not just on the chair, but on its surroundings and their interaction. Chairs are context dependent. Everything in physics is context dependent.
The typical reaction to this problem is to look for entities and interactions that remain the same in every context. Yes, whether we have water, water vapor or ice depends on the external temperature and pressure, phase of matter is context dependent, but there are always water molecules and electromagnetic forces between them. In fact, this explains why we have the different phases of water in different conditions. Yes, we may have water molecules or molecular oxygen/hydrogen depending on external conditions, but there are always oxygen and hydrogen atoms mediated by electromagnetic forces. In fact, this explains in which context we have the different configurations. What we need to do, then, is simply to find the “true” intrinsic object that the universe is made of, and we are done. The theory of everything. But will this work?
The first hint of a problem is that the issue of contextuality is never really solved at any level, it is just handed off to the next one. Yes, water molecules exist in a bigger context than ice or water vapor, but they too have a limited context and can transform into molecular oxygen/hydrogen. Even what we call fundamental particles can transform into one another: a magnetically trapped positron will remain a positron indefinitely, but it will not remain so for long if it is surrounded by standard matter. In this case, there is no underlying level: we do not understand positron-electron annihilation as the rearrangement of some other well-defined objects that are left unchanged within the transition.
