No, I think he really did mean “eminent.” Immanent, imminent, and eminent are all English words, but eminent does seem to fit in this quote just fine.
See my post 78, for my opinion on the matter.
Try this. Go to your favorite search engine and type in, ‘eminently practical’. Mine gave me no direct hits, just one word or the other.
Then type in ‘immanently practical’. I got more hits for that exact quote than I could count. Now you may not find that dispositive but I do. Usage determines the meaning of words. ‘Eminent’ isn’t used the way Ayers used it; ‘immanent’ is.