Full Idea
When a certain number of logical principles have been admitted as self-evident, the rest can be deduced from them; but the propositions deduced are often just as self-evident as those that were assumed without proof.
Gist of Idea
Some propositions are self-evident, but their implications may also be self-evident
Source
Bertrand Russell (Problems of Philosophy [1912], Ch.11)
Book Reference
Russell,Bertrand: 'The Problems of Philosophy' [OUP 1995], p.65
A Reaction
This seems an important corrective to the traditional rationalist dream, based on Euclid, that all knowledge is self-evident axioms followed by proofs of the rest. But Russell here endorses a more sensible sort of rationalism.