Full Idea
Every animal instinctively strives for an optimum of favourable conditions under which it can expend all its strength and achieve its maximal feeling of power; every animal abhors ...every hindrance that obstructs this path to the optimum.
Gist of Idea
All animals strive for the ideal conditions to express their power, and hate any hindrances
Source
Friedrich Nietzsche (On the Genealogy of Morals [1887], III.§07)
Book Reference
Nietzsche,Friedrich: 'On the Genealogy of Morals/ Ecce Homo', ed/tr. Kaufmann,Walter [Vintage 1969], p.107
A Reaction
This became the lynchpin of Nietzsche's account of the source of values. It is a highly naturalistic view, fitting it into evolutionary theory (thought running deeper than that), so I have a lot of sympathy with the view.