These eagles often target various arboreal or ground-dwelling mammals and birds, which are often unsuspectingly ambushed in such dense, knotty environments.
Much yew is knotty and twisted, and therefore unsuitable for bowmaking; most trunks do not give good staves and even in a good trunk much wood has to be discarded.
Pointing to the knotty nature of materialism, existentialism and hedonism he leads the reader to the path of spiritual bliss through rational knowledge, rational perception and rational conduct.