Full Idea
No external factors seem to be required for Fred's belief that he is in pain, or that he exists, or that there are no unicorns.
Gist of Idea
Pain, our own existence, and negative existentials, are not external
Source
Jaegwon Kim (Philosophy of Mind [1996], p.198)
Book Reference
Kim,Jaegwon: 'Philosophy of Mind' [Westview 1998], p.198
A Reaction
This is an extremely important observation for anyone who was getting over-excited about external accounts of content. Unicorns might connect externally to horns and horses.