Did not expect to see William James pop up on HN.
If you're interested in philosophy (especially epistemology), the pragmatists were a fascinating offshoot.
https://en.m.wikipedia.org/wiki/William_James
IMHO they were a reasonable response to the irreducible complexity that accreted as a result of applying increasingly specific and complex empiricism to questions far broader than it might be suited to. (E.g. How do we know anything?)