Full Idea
A creature that knows what makes its thoughts true and what would cause it to have them, could therefore cause itself to have true thoughts. …This would explain why experimentation is so close to the heart of our cognitive style.
Gist of Idea
We can deliberately cause ourselves to have true thoughts - hence the value of experiments
Source
Jerry A. Fodor (The Elm and the Expert [1993], §4)
Book Reference
Fodor,Jerry A.: 'The Elm and the Expert' [MIT 1995], p.92