Full Idea
If pleasure, displeasure, sensation, memory, reflex movements are all part of the essence of matter, then human knowledge penetrates far more deeply into the essence of things.
Gist of Idea
If some sort of experience is at the root of matter, then human knowledge is close to its essence
Source
Friedrich Nietzsche (Unpublished Notebooks 1872-74 [1873], 19 [161])
Book Reference
Nietzsche,Friedrich: 'Unpublished of 'Unfashionable Obs' period (v 11)', ed/tr. Gray,Richard T. [Stanford 1995], p.52
A Reaction
I don't think Nietzsche is thinking of monads at this point, but his idea certainly applies to them. Leibniz rested his whole theory on the close analogy between how minds work and how matter must also work.