Full Idea
The essence of individuality always eludes words and baffles description, and is for that very reason irrelevant to science.
Gist of Idea
The essence of individuality is beyond description, and hence irrelevant to science
Source
Bertrand Russell (Introduction to Mathematical Philosophy [1919], VI)
Book Reference
Russell,Bertrand: 'Introduction to Mathematical Philosophy' [George Allen and Unwin 1975], p.61
A Reaction
[context needed for a full grasp of this idea] Russell seems to refer to essence as much as to individuality. The modern essentialist view is that essences are not beyond description after all. Fundamental physics is clearer now than in 1919.