Although I am, by and large, a positivist
, I believe that assuming physical equations to be true (rather than simply observing that it seems to predict experimental data) can be useful in assessing their philosophical significance.
For instance, take the Schrodinger wave equation:
-((h/2π)2/2m)(∂2ψ(x)/∂x2)+V(x)ψ(x) = Eψ(x)
If we take the potential energy, V, to be 0 everywhere (i.e. the particle is not being acted upon by its environment), the equation becomes:
-((h/2π)2/2m)(∂2ψ(x)/∂x2) = Eψ(x)
Valid solutions for ƒÕ(x) include Asin(cx) and Bcos(cx). We'll use Asin(x). However, since both sin and cos functions "look" the same everywhere, we find we have no useful information about the particle. The particle has an equal likelihood of existing anywhere; since it's probability of existence is 1 and it has an equal probability of existing anywhere in infinite space, it essentially does not exist. (i.e. 1/infinity = 0)
This can be interpreted as meaning that all particles can be said to exist only as they relate to other particles. An atom's existence is contingent on its interactions with other atoms. Furthermore, since potential energy is almost always dependent on distance, an object's distance from everything else in the universe actually has an effect on the probability of that object's existence.
It was only in writing this that I realized a more profound philosophical significance to this. While there are numerous interactions WITHIN an atom (between quarks, protons, neutrons, electrons, etc.), the atom still cannot be said to exist if all the interactions occur within it. A component of the atom cannot act upon the whole atom, since it cannot act upon itself. Thus, the existence of a system is dependent on what lies outside the system.
This leads to a rather profound paradox when one takes the universe to be the system. If the universe is all that is, how can it exist without something else to define a potential for the universe?
The simplest solution to this paradox would be to claim that the Schrodinger wave equation is not true, or is simply a simplification, which I believe is its current status in physics.