Full Idea
The relation of whole and part is, it would seem, an indefinable and ultimate relation, or rather several relations, often confounded, of which one at least is indefinable.
Gist of Idea
The part-whole relation is ultimate and indefinable
Source
Bertrand Russell (The Principles of Mathematics [1903], §135)
Book Reference
Russell,Bertrand: 'Principles of Mathematics' [Routledge 1992], p.138
A Reaction
This is before anyone had produced a mathematical account of mereology (qv).