Full Idea
The knowledge of things by their causes, which is often given as a definition of rational knowledge, is useless unless the causes converge to a minimum number, while still producing the maximum number of effects.
Gist of Idea
Understanding by means of causes is useless if they are not reduced to a minimum number
Source
William James (The Sentiment of Rationality [1882], p.21)
Book Reference
James,William: 'Selected Writings of William James', ed/tr. Bird,Graham [Everyman 1995], p.21
A Reaction
This is certainly the psychological motivation for trying to identify 'the' cause of something, but James always tries to sell such things as subjective. 'Useless' to one person is a subjective criterion; useless to anyone is much more objective.
Related Idea
Idea 13929 Natural explanations give the causal interconnections [Haslanger]