Patrick Reany:

[...]

describe or explain the behavior of the material world. We cannot help
feeling that this is meant to imply the existence of such a world,
though what the adjective "material" here means is by no means clear.
The physicist has been striving for years to attach a clear meaning to
the term matter, and undoubtedly we have reason to believe that the
concept means much more to us today than to the physicists of fifty
years ago. However, to have a clear understanding of a physical
concept like matter is not at all equivalent to the assumption that
there is a "real" world behind our sense-perceptions which is
responsible for the existence of matter.

Allow me to mention what weinberg said in this regard at a talk of his I
attended a while back. His point of view regarding a "theory of everything",
was that it would not be a very satisfactory theory unless it gave one
confidence that one really understood what was going on in the universe
and did something more than simply produce the correct numbers.