Full Idea
There could be no intentional zombie, because (unlike with a conscious agent) there simply is no fact of the matter as to exactly which aspectual shapes its alleged intentional states have. Is it seeking water or H2O?
Clarification
An 'aspectual shape' is Searle's term for a way of seeing something
Gist of Idea
Without internal content, a zombie's full behaviour couldn't be explained
Source
John Searle (The Rediscovery of the Mind [1992], Ch. 7.III)
Book Reference
Searle,John R.: 'The Rediscovery of the Mind' [MIT 1999], p.163
A Reaction
The obvious response to this is behaviourist talk of 'dispositions'. The dispositions of scientist when seeking water and when seeking H2O are different. Zombies behave identically to us, so their intentional states have whatever is needed to do the job.