I was listening to a debate today between Frank Turek and Jeffery Jay Lowder. The debate topic was about whether Theism or Naturalism is the best explanation of the world. Lowder defended the Naturalistic view point, and I thought he gave one of the more powerful cases for philosophical Naturalism I have seen in a debate format. Usually atheists and naturalists get slaughtered by theists. In this debate I think Lowder probably won, or at least tied Turek in the debate.
One of the things that Lowder thought Naturalism explained better than theism was the existence of the material world. I found this rather odd, because I am currently reading the book A World For Us: A Case for Phenomenalistic Idealism. What becomes very apparent in the book is that it isn't exactly clear what the material world actually is, in fact in the book Foster (John Foster is the author) points out that there are some real issues for the realist about the physical world. First, the physical realist has a problem accounting for the intrinsic content of objects in the world. Intrinsic content are things that do not make up dispositional properties. Natural science only takes into account the spatial and dispositional qualities of objects in the world. Science leaves untouched questions of how colors appear to us for instance. In fact science chooses to treat such notions as causally impotent, and less real. In fact, intrinsic content is the same thing as secondary qualities. Secondary qualities are things like sight, smell, being appeared to in a blue way, etc. Simply put the way the color blue appears to you or me isn't the same as what science says blue is.
This problem of the gap between qualia empirical qualities and natural science gives rise to a very real worry. How is it that our everyday perceptions can be said to be true. It gets even worse, all of our scientific research comes from our conscious experience, so there isn't any getting "behind" our perception. The best that we can do is ferret out a geometrical structure of reality, but this is far from what is commonly meant by "physical reality".
We can also take the Berkeleyan claims seriously here. Berkeley noted that there isn't a difference between primary qualities like hardness and extension and secondary qualities like color, taste, smell etc. Locke and other enlightenment philosophers tried to argue that secondary qualities were mind dependent, but that primary qualities were not. This isn't true, because all of our access to the external world comes through sensation, which are ideas in the mind, and hence fundamentally mental.
This is before we even get to actual scientific theories like Quantum Mechanics, which undermines the whole notion of "matter" and takes them to be waves of some sort. In fact, some scientists even say that space-time isn't fundamental. For these reasons, if someone like Lowder wants to argue that Naturalism explains the existence of matter better than theism, then we need to know what exactly matter is, which is not something that can be given an adequate accounting.