Full Idea
Intentional systems don't really have beliefs and desires, but one can explain and predict their behaviour by ascribing beliefs and desires to them. This strategy is pragmatic, not right or wrong.
Clarification
'Intentional systems' think about things
Gist of Idea
Beliefs and desires aren't real; they are prediction techniques
Source
Daniel C. Dennett (Brainstorms:Essays on Mind and Psychology [1978], p.7?)
Book Reference
Rey,Georges: 'Contemporary Philosophy of Mind' [Blackwell 1997], p.77
A Reaction
If the ascription of beliefs and desires explains behaviour, then that is good grounds for thinking they might be real features of the brain, and even if that is not so, they are real enough as abstractions from brain events, like the 'economic climate'.