Section 15 provides textual evidence from early Christian writings, particularly Tertullian, to show hatred and ressentiment being paraded as "Christian love." These writers expend a great deal of voyeuristic energy inventing all sorts of tortures for sinners not welcomed into the kingdom of heaven.
Nietzsche concludes with the remark that the struggle between "good and evil" and "good and bad" is one of the oldest and greatest on earth, and that the "good and evil" of ressentiment has unquestionably come out on top. He asks, however, if there might be a resurgence of the overthrown master morality, suggesting that we might will this with all our might.
One of the greatest deceptions of language, according to Nietzsche, is the subject-predicate form of grammar. Because all sentences are divided into a subject and a predicate, we are led to believe that there are actors (subjects) and deed (predicates) and that the two can be separated. As a result, we come to think of killing as something distinct from a bird of prey, something that it does. Nietzsche points out that grammar would similarly suggest to us that flashing is something distinct from lightning, something that it does. And just as there is no lightning distinct from the flash, Nietzsche suggests that there is no bird of prey distinct from the killing.
This argument does not simply suggest that killing is in a bird of prey's "nature" and that "it wouldn't be a bird of prey if it didn't kill things." In Nietzschean metaphysics, there is no such thing as the bird of prey as common wisdom would understand it. Gilles Deleuze interprets Nietzsche as suggesting that nothing exists but forces. We might simplify Deleuze's analysis by suggesting that only verbs truly exist: nouns and subjects are just the conveniences of grammar. While we might talk about a bird of prey killing a lamb, really there is just one force acting upon another. Of course, using "force" as a noun is a mistake, as it simply substitutes one noun for another.
This discussion of metaphysics gets very tricky very quickly, and because we are so accustomed to thinking in terms of subjects and predicates, it is very difficult to imagine a world that consists solely of forces acting on one another. Rather than dwell too long on this question, we leave the metaphysics here, encouraging the reader to sort out what consequences this metaphysics might have on our concept of personal identity, epistemology, and much else besides, and to ask whether Nietzsche's account is plausible and how it might be tested. For now, we will focus on the immediate consequences for the moral philosophy Nietzsche is discussing in this essay.
At first glance, it might appear that Nietzsche is denying free will: we cannot hold the bird of prey accountable since it could not act otherwise. On this interpretation, Nietzsche would essentially be claiming that none of us are free to do anything and none of us can be held accountable for anything. This interpretation is about 10% true. To claim that the bird of prey has no free will is about as opposite to Nietzsche's position as can be. Nietzsche would rather claim that there is no bird of prey independent of its will. To talk about a bird of prey as "having" free will is again to make the subject- predicate error. Will is not a "thing" that one "has": a will is, essentially, what one is. The bird of prey is its will, and that will wills the death of the lamb. Not to kill the lamb would require a different will, that is, a different creature altogether. If we say the bird of prey should not have killed the lamb, we are saying that the bird of prey should have been a different animal.