Nietzsche suggests that the "slave revolt in morality" begins when ressentiment, or resentment, becomes a creative force. Slave morality is essentially negative and reactive, originating in a denial of everything that is different from it. It looks outward and says "No" to the antagonistic external forces that oppose and oppress it. Master morality, on the other hand, concerns itself very little with what is outside of it. The low, the "bad," is an afterthought and is noticed only as a contrast that brings out more strongly the superiority of the noble ones.
While both slave and master morality can involve distortions of the truth, master morality does so far more lightly. Nietzsche notes that almost all the ancient Greek words denoting the lower orders of society are related to variants on the word for "unhappy." The nobles saw themselves as naturally happy, and any misunderstanding rested on the contempt and distance they held from the lower orders. By contrast, the man of ressentiment distorts what he sees so as to present the noble man in as bad a light as possible, and thereby to gain reassurance.
The noble man is incapable of taking seriously all the things that fester and build in the man of ressentiment: accidents, misfortunes, enemies. In allowing resentment and hatred to grow in him, in having to rely on patience, secrets, and scheming, the man of ressentiment ultimately becomes cleverer than the noble man. This constant brooding and obsession with ones enemies begets the greatest invention of ressentiment: evil. The concept of the "evil enemy" is basic to ressentiment just as "good" is basic to the noble man. And just as the noble man develops the concept of "bad" almost as an afterthought, so is the concept of "good" created as an afterthought by the man of ressentiment to denote himself.
Nietzsche remarks on how different the concepts of "evil" and "bad" are, in spite of both being considered the opposite of "good." He explains this difference by explaining that there are two very different concepts of "good" at work: The noble man's "good" is precisely what the man of ressentiment calls "evil."
Among their own kind, noble men are respectful and subdued, but when they venture out among strangers, they become little more than uncaged beasts-- "blonde beasts," as Nietzsche calls them. "Blonde" here is a reference to lions rather than to hair color, as Nietzsche bestows this name not only on Vikings and Goths, but also on Arab and Japanese nobility. The name "barbarian" is often associated with the violence that occasionally erupts from noble people.
Contemporary wisdom would suggest some sort of progress and refinement from these "blonde beasts" to the humanity of today, but Nietzsche vehemently disagrees. The overthrow of master morality in favor of slave morality is nothing to be proud of. These barbarians may have been fearful, but they were also admirable. Today's world of ressentiment is neither: it is merely mediocre. Nietzsche characterizes the nihilism he detests in contemporary society as a weariness with humanity. We no longer fear humanity, but we also no longer have hopes for, reverence of, or affirmation of humanity. Nietzsche fears that our slave morality has rendered us insipid and dull.
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.