Dualism is the belief that there are separate physical and
non-physical aspects of reality. This leads to the famous mind-body
problem: if part of us is physical, and part non-physical, how do they
interact? "Where" are they connected?
I don't claim to have the answer to that (although I do have
or two about it), but think it's still better
than the other main alternatives: Idealism and Materialism/Physicalism/Scientism.
So, I believe that if one is both a scientist and believes in any kind
of spirituality, one is actually a dualist.
For an entertaining general description of philosophy, see
The Big Dummy's Guide to Theology, Philosophy, and Ethics.
Sept. 2002: This link finally works again; I found its new home!