Full Idea
The only classes appear to be things, predicates and relations.
Gist of Idea
The only classes are things, predicates and relations
Source
Bertrand Russell (The Principles of Mathematics [1903], §440)
Book Reference
Russell,Bertrand: 'Principles of Mathematics' [Routledge 1992], p.467
A Reaction
This is the first-order logic view of reality, which has begun to look incredibly impoverished in modern times. Processes certainly demand a hearing, as do modal facts.