Full Idea
All our knowledge, both knowledge of things and knowledge of truths, rests upon acquaintance as its foundations.
Clarification
'Acquaintance' is direct awareness
Gist of Idea
All knowledge (of things and of truths) rests on the foundations of acquaintance
Source
Bertrand Russell (Problems of Philosophy [1912], Ch. 5)
Book Reference
Russell,Bertrand: 'The Problems of Philosophy' [OUP 1995], p.26
A Reaction
Russell here allies himself with Hume, and with the empiricist version of foundationalism. 'Acquaintance' plays the role which 'impressions' played for Hume. He is eliminating any possible cognitive content from the Hume idea, implying pure sense-data.