Full Idea
The chief importance of knowledge by descriptions is that it enables us to pass beyond the limits of our private experience.
Gist of Idea
Knowledge by descriptions enables us to transcend private experience
Source
Bertrand Russell (Problems of Philosophy [1912], Ch. 5)
Book Reference
Russell,Bertrand: 'The Problems of Philosophy' [OUP 1995], p.32
A Reaction
The most basic question for empiricism concerns how we can know things beyond immediate experience. Russell is right, though this doesn't tell us much. We need to know the rules for valid descriptions, explanation, speculations etc.