Wolfram is proposing a radically different way of interpreting the universe. His main argument is that if his cellular automatons can achieve emergent behaviour similar to real physics, then it is evidence for it being the underlying mechanism in the universe.

For a (really long) discussion on how this simulation parallels physics, check his book, A New Kind of Science, out.

Then maybe you would want to read Aaronson's review of it, just for a balanced perspective.