Full Idea
Any broadly materialistic metaphysical position needs to claim that physics is causally complete.
Gist of Idea
Materialism requires that physics be causally complete
Source
Terence Horgan (From Supervenience to Superdupervenience [1993], §6)
Book Reference
-: 'Mind' [-], p.19
A Reaction
Since 'physics' is a human creation, I presume he means that physical reality is causally complete. The interaction problem that faced Descartes seems crucial - how could something utterly non-physical effect a physical change?