For Nietzsche, morality is a reversal of instincts, that it is a "will to self-tormenting" as a "repressed cruelty" which has emerged as a response to the civilization and enclosure within walls of humankind (section 22, p. 528). This stands in general accord with Nietzsche's conception of adaptation and the effect of accident: what was once an adaptation becomes, when it is no longer a necessity for survival, a sublimated instinct which is reassessed, reinterpreted, and realigned in a way which does not necessarily show its origins. Especially tied to this is the creation of the concept of guilt; here, Nietzsche clearly stands as a precursor for future philosophers (here, Foucault is obvious) in his historical analysis of a seemingly absolute phenomenon in terms of historical factors. Guilt, for Nietzsche, emerged from the very real relations between creditor and debtor; ultimately, through accident, reinterpretation, and changing conditions, guilt moved from a state between individuals to a state between the individual and society. Eventually, this relation became one between the state and individual. The purpose of punishment changes from a recompense in a more monetary sense to one in which power is vented, in which one becomes master over the other (section 12, p. 513). And here, the tie between punishment and guilt ties to cruelty and morality; guilt is the creation of the conquerors, those who would make laws and exert their master over others. Through guilt, they exercise their cruelty over others, in a celebratory fashion, binding others to laws and, hence, to civilization. Morality, in this sense, stands somewhat as an internalization of guilt, a creation which arose from the origins of law, an internalized reaction to external laws (section 17).
This results in a further turn, however, one which Nietzsche laments: guilt becomes internalized and turned back against those who were originally creditors. Hence, slave morality becomes endemic (for there can be no doubt that the debtor is the slave, and hence, a reactive type) and ressentiment becomes the order of the day (section 21).