Full Idea
The relation involved in judging or believing must, if falsehood is to be duly allowed for, be taken to be a relation between several terms, not between two.
Gist of Idea
In order to explain falsehood, a belief must involve several terms, not two
Source
Bertrand Russell (Problems of Philosophy [1912], Ch.12)
Book Reference
Russell,Bertrand: 'The Problems of Philosophy' [OUP 1995], p.72
A Reaction
His point is that if a belief relates to one object ('D's love for C') it will always be true. Russell is trying to explain what goes wrong when we believe a falsehood. It is not clear how the judgement 'x exists' involves several terms.