Nietzsche opens by expressing dissatisfaction with the English psychologists who have tried to explain the origin of morality. They claim to be historians of morality, but they completely lack a historical spirit. Their theories suggest that, originally, people benefiting from the unegoistic actions of others would applaud those actions and call them "good." That is, initially, what was good and what was useful were considered one and the same. Over time, these genealogists suggest, we forgot this original association, and the habit of calling unegoistic actions "good" led us to conclude that they were somehow good in and of themselves.
Nietzsche disagrees with this account, suggesting that those to whom "goodness" was shown did not define "good." Rather, it was the "good" themselves--the noble and the powerful--who defined the term. They came to see themselves as good when they came to see the contrast between themselves and those who were below them: the common people, the poor and the weak. Their position of power included the power over words, the power to decide what would be called "good" and what "bad."
In support of his argument, Nietzsche remarks on the similarity between the German word for "bad" and the words for "plain" and "simple." By contrast, he notes, in most languages, the word for "good" derives from the same root as the words for "powerful" or "masters" or "rich." In the Greek, Nietzsche notes that "good" is associated also with "truth." The low, poor, commoners, are then associated with lying and cowardice.
Nietzsche also remarks on how "dark" and "black" are used as negative terms, presumably because of the dark-haired peoples of Europe who were overrun by blonde, Aryan conquerors. He notes the association of "good" with "war" and "warlike."
Nietzsche then considers the change in language that takes place when the priestly caste gains power. Here, "pure" and "impure" become opposites associated with "good" and "bad." This "pureness" consists in an abstinence from sex, from fighting, and from certain foods, a renouncement of many of the noble warrior's habits. With these priests, everything becomes more dangerous: they alternate between brooding and emotional outbursts, and their wills are much stronger and sharper. But Nietzsche also remarks that only with the priests do human beings become interesting. With the priests, the human soul first gains those attributes that set it apart from animals: it acquires depth and becomes evil.
Though the priestly mode of evaluation springs from the knightly-aristocratic mode, it becomes its opposite, and its most hated enemy. Because the priests are impotent, they learn to hate, and their hate becomes more powerful than any of the warlike virtues lauded by the nobles. Nietzsche identifies the Jews as the finest example of the priestly caste, the most refined haters in human history. The Jews managed to effect a complete reversal in moral valuations, associating themselves, the poor, the wretched, the meek, with "good," and the lustful, powerful, and noble as "evil," damned for all eternity.