Full Idea
The possession of true thoughts means everywhere the possession of invaluable instruments of action.
Gist of Idea
True thoughts are just valuable instruments of action
Source
William James (Pragmatism - eight lectures [1907], Lec 6)
Book Reference
James,William: 'Pragmatism - eight lectures' [Dover 1995], p.78
A Reaction
It looks to me like we should distinguish 'active' and 'passive' instrumentalism. The passive version says there is no more to theories and truth than what instruments record. James's active version says truth is an instrument for doing things well.