What Are the Limits of Physics?

Contrary to the disciples of scientism, physics has limits. Philosopher Ed Feser gives a quick run-down which is worth passing along. Feser writes,

As I have emphasized many times, what physics gives us is a description of the mathematical structure of physical reality.  It abstracts from any aspect of reality which cannot be captured via its exclusively quantitative methods. (emphasis added)

Let’s stop here because this is important. What Feser is saying is that when the methods of physics are applied to any object, any event, any piece of the world around us, the method only addresses the parts of that object, event, or piece of the world that can be mathematically quantified. Physics ignores any parts of the world that cannot be mathematically quantified.

One reason that this is crucial to keep in mind is that from the fact that something doesn’t show up in the description physics gives us, it doesn’t follow that it isn’t there in the physical world.  This is like concluding from the fact that color doesn’t show up in a black and white pen and ink drawing of a banana that bananas must not really be yellow.

In both cases the absence is an artifact of the method employed, and has nothing whatsoever to do with the reality the method is being used to represent.  The method of representing an object using black ink on white paper will necessarily leave out color even if it is there, and the method of representing physical reality using exclusively mathematical language will necessarily leave out any aspect of physical reality which is not reducible to the quantitative, even if such aspects are there.

But maybe all of reality is just composed of mathematical structure. Feser argues that this cannot be the case, that other aspects of reality must be there.

The quantitative description physics gives us is essentially a description of mathematical structure.  But mathematical structure by itself is a mere abstraction.  It cannot be all there is, because structure presupposes something concrete which has the structure.  Indeed, physics itself tells us that the abstraction cannot be all there is, since it tells us that some abstract mathematical structures do not fit the actual, concrete material world.

For example, Einstein is commonly taken to have shown that our world is not really Euclidean.  This could only be true if there is some concrete reality that instantiates a non-Euclidean abstract structure rather than a Euclidean abstract structure.  So, physics itself implies that there must be more to the world than the abstract structure it captures in its purely mathematical description, but it does not and cannot tell us exactly what this concrete reality is like.

Physics is one tool, a powerful one certainly, in our toolbox for describing reality. But to think that it is the only tool in the toolbox is just silly.