Full Idea
We can even say that, in all such knowledge as can be expressed in words, with the exception of 'this' and 'that' and a few other words of which the meaning varies on different occasions - no names occur, but what seem like names are really descriptions.
Gist of Idea
Names are really descriptions, except for a few words like 'this' and 'that'
Source
Bertrand Russell (Introduction to Mathematical Philosophy [1919], XVI)
Book Reference
Russell,Bertrand: 'Introduction to Mathematical Philosophy' [George Allen and Unwin 1975], p.178
A Reaction
I like the caveat about what is expressed in words. Russell is very good at keeping non-verbal thought in the picture. This is his famous final reduction of names to simple demonstratives.