My awareness of Russell's hypotheses is admittedly skeletal. What I've seen of it has been overwhelmingly a priori
, though. Descartes had a lot of people going this way for a long time. A smart person (Russell undoubtedly was one) can do a lot when there's nothing but words and ideas to deal with. But what happens when you design and experiment to test your hypothesis, get experimental data and analyze it? I didn't see much of that with Russell, but again, I haven't looked into him with any depth. If you know of experiments he designed and conducted to test his own hypotheses, please link me to them. I do not deny that his ideas (those that I've seen so far) are thought-provoking.