Russell gives too much credit to radical empiricism fails to warn against the dangers of going too far in the direction of radical empiricism, which is really just as bad as radical rationalism.
Philosophers came to be divided into two camps: those who claimed that man obtains his knowledge of the world by deducing it exclusively from concepts, which come from inside his head and are not derived from the perception of physical facts (the Rationalists)—and those who claimed that man obtains his knowledge from experience, which was held to mean: by direct perception of immediate facts, with no recourse to concepts (the Empiricists). To put it more simply: those who joined the mystics by abandoning reality—and those who clung to reality, by abandoning their mind.
FTNI, by Ayn Rand
I wasn't trying to endorse the whole empiricist philosophy, and neither was Russell, at least in this quote. The rationality lesson it offers is not "radical empiricism good, radical rationalism bad" but more like "a wide base of principles with connections to experience good, a small base of abstract logical principles bad".
Here's the new thread for posting quotes, with the usual rules: