The universe may be unknowable in principle

A significant number of scientists are worried that we may be at the end of science because the universe may simply be unknowable. Here's how Lawrence Krauss put it.

[P]hysicists have been exploring the idea that perhaps physics is an 'environmental science', that the laws of physics we observe are merely accidents of our circumstances, and that an infinite number of different universe could exist with different laws of physics.

This is true even if there does exist some fundamental candidate mathematical physical theory. For example, as is currently in vogue in an idea related to string theory, perhaps the fundamental theory allows an infinite number of different 'ground state' solutions, each of which describes a different possible universe with a consistent set of physical laws and physical dimensions.

It might be that the only way to understand why the laws of nature we observe in our universe are the way they are is to understand that if they were any different, then life could not have arisen in our universe, and we would thus not be here to measure them today.

This is one version of the infamous "anthropic principle". But it could actually be worse — it is equally likely that many different combinations of laws would allow life to form, and that it is a pure accident that the constants of nature result in the combinations we experience in our universe. …

In this case, the end of "fundamental" theoretical physics … might occur not via a theory of everything, but rather with the recognition that all so-called fundamental theories that might describe nature would be purely "phenomenological", that is, they would be derivable from observational phenomena, but would not reflect any underlying grand mathematical structure of the universe that would allow a basic understanding of why the universe is the way it is.