The difference is that "the principle that science can study only
the things that are accessible to its instruments and techniques"
has nothing to do with whether "nature is all there is".
Or, to put it another way, the instruments and techniques of science
cannot determine whether or not "nature is all there is". A scientist
is certainly free to assume that nature is all there is if they so
choose, but this assumption has nothing to do with "the principle that
science can study only the things that are accessible to its instruments
and techniques".
No offense intended, but I suspect that you might be confusing
methodological naturalism with scientism. For example, the following
appeared earlier in this thread:
>>BH>I continue to be confused in the way that several use the term
>>methodological naturalism. Can anyone point to some references
>>wherein this term is defined?
>
>SJ>Johnson defines MN as:
>
>"A variety of terms have been used in the literature to designate the
>philosophical position I call scientific naturalism. For present
>purposes, the following terms may all be considered, equivalent:
>scientific naturalism, evolutionary naturalism, scientific
>materialism, and scientism. All these terms imply that scientific
>investigation is either the exclusive path to knowledge or at least
>by far the most reliable path, and that only natural or material
>phenomena are real. In other words, what science can't study is
>effectively unreal." (Johnson P.E., "Darwin on Trial", 1993, p116).
>
>But I would have thought that definition is hardly necessary in this
>case - the words define themselves. The only *method* to be used in
>science is *naturalism*, and "naturalism" is the assumption that
>"nature is all there is".
>
In the pasage you quoted Johnson was defining scientism rather than
methodological naturalism.
Brian Harper
Associate Professor
Applied Mechanics
Ohio State University
"Aw, Wilbur" -- Mr. Ed