From Victor Reppert:
I am convinced that a broadly materialist view of the world must possess three essential features.
First, for a worldview to be materialistic, there must be a mechanistic base level.
Second, the level of basic physics must be causally closed.
Third, whatever is not physical, at least if it is in space and time, must supervene on the physical.
This understanding of a broadly materialistic worldview is not a tendentiously defined form of reductionism; it is what most people who would regard themselves as being in the broadly materialist camp would agree with, a sort of “minimal materialism.”
To the atheists:
Some of you know you’re materialists, some of you suspect it, others try to deny it or don’t like to be identified as such. But if you’re an atheist what else do you have?