Full Idea
Empty terms and concepts provide the largest problem for the externalist thesis of the world dependence of concepts.
Gist of Idea
Externalism can't explain concepts that have no reference
Source
Gabriel M.A. Segal (A Slim Book about Narrow Content [2000], 2.2)
Book Reference
Segal,Gabriel M.A.: 'A Slim Book about Narrow Content' [MIT 2000], p.31
A Reaction
A speculative concept could then become a reality (e.g. an invention). The solution seems to be to say that there is an internal and an external component to most concepts.