Full Idea
I define 'naturalism' as the hypothesis that the world of space-time is all that there is.
Gist of Idea
'Naturalism' says only the world of space-time exists
Source
David M. Armstrong (Truth and Truthmakers [2004], 09.1)
Book Reference
Armstrong,D.M.: 'Truth and Truthmakers' [CUP 2004], p.112
A Reaction
This is helpful, because it doesn't mention the nature of the physical matter contained in space-time, leaving theories like panpsychism as possible naturalistic theories. Galen Strawson, for example.