Full Idea
Scientists …do not defend any belief more strongly than that the strong are free to be weak, and the birds of prey are free to be lambs: - in this way, they gain the right to make the birds of prey responsible for being birds of prey.
Gist of Idea
If we say birds of prey could become lambs, that makes them responsible for being birds of prey
Source
Friedrich Nietzsche (On the Genealogy of Morals [1887], I.§13)
Book Reference
Nietzsche,Friedrich: 'On the Genealogy of Morals', ed/tr. Diethe, Carol [CUP 1997], p.26
A Reaction
This is a flat rejection of the Sartrean idea that we can what sort of person we want to be. He cares about birds of prey, but also lambs can't become eagles. I would say that adolescents have a reasonable degree of choice about what they will become.
Related Idea
Idea 3844 Existentialism says man is whatever he makes of himself [Sartre]