Elsewhere, Nietzsche, with no further physiological consideration for the notion of the body, attributes a purely social origin to morality: Wherever we encounter a morality, we also encounter valuations and an order of rank of human impulses and actions. These valuations and orders of rank are always expressions of the needs of a community and herd: whatever benefits it most—and second most, and third most—that is also considered the first standard for the value of all individuals. Morality trains the individual to be a function of the herd and to ascribe value to himself only as a function. The conditions for the preservation of different communities were very different; hence there were very different moralities. […] Morality is herd instinct in the individual ¹.

Here we can see that physiology is no longer the perspective Nietzsche chooses: the "herd instinct" is not a matter of the body, specific to each individual, but represents a purely social instinct. It is no longer because I am weak that I choose a particular moral, but because society has chosen it, and as a member of that society, I also adopt it.

Finally, Nietzsche attributes the origin of Christian morality to a psychological feeling: resentment (which could be defined as the evil anger of feeling one's own weakness and envious jealousy towards those who are not): The slave revolt in morality begins when the ressentiment itself becomes creative and gives birth to values: the ressentiment of those beings who are prevented from a genuine reaction, that is, something active, and who compensate for that with a merely imaginary vengeance ². Resentment leads the weak to create morality, i.e. the condemnation of the freedom and self-assertion of the powerful people, and is therefore the origin of morality.

These three origins are in fact linked, of course: psychological resentment comes from the physiological weakness of my body, and likewise I can only want to receive my morality from society because I am so physiologically weak that I cannot leave the herd. The concept that links these three approaches, and which ultimately constitutes the true origin of morality, is that of self-interest.

If I adopt this or that moral code, it is because it is in my own interest to do so. If I am humble, it is because it is in my interest, as a weak person, not to be arrogant, so as not to provoke the blows of the powerful people: When stepped on, a worm doubles up. That is clever. In that way, he lessens the probability of being stepped on again. In the language of morality: humility ³.

It is in my interest both to be moral because I am physiologically weak and because otherwise society will punish me for my immorality. Resentment is the psychological sign that I am moral only out of self-interest and not out of any real love of morality: jealousy of the powerful shows that I would like to be amoral like them.

c/ Criticism of Nietzschean genealogy

Thanks to Nietzsche, we have perhaps identified the origin of morality - and ultimately also of religion: interest. It is in my interest to be moral and for there to be a God. We can concede that to Nietzsche. But he does not just affirm this origin; he gives it the status of a foundation. In other words, the origin of morality is at the same time its foundation (by the foundation of an idea, I mean, according to the two possible meanings, its truth or its value).

Let us look at exactly how Nietzsche shifts from the origin to the foundation of morality.

Nietzsche begins by showing that he does in fact distinguish between the two questions: Basically even then the real concern for me at heart was something much more important than coming up with hypotheses about the origin of morality, either my own or from other people (or, more precisely stated—this latter issue was important to me only for the sake of a goal to which it was one path out of many). For me the issue was the value of morality—and in that matter I had to take issue almost alone with my great teacher Schopenhauer ⁴.

He thus asserts that grasping the origin of morality is only secondary to a far more ambitious project: grasping its value - or its foundation. So much so that Nietzsche asserts that if the origin of morality were an error (for example, the opinion a people might have about its morality), this would not diminish its value: But the worth of a precept, "Thou shalt," is fundamentally different from and independent of such opinions about it, and must be distinguished from the weeds of error with which it has perhaps been overgrown: just as the worth of a medicine to a sick person is altogether independent of the question whether he has a scientific opinion about medicine, or merely thinks about it as an old wife would do. A morality could even have grown out of an error: but with this knowledge the problem of its worth would not even be touched ⁵.

And yet, as we read on, we cannot but realise the obvious: Nietzsche never moves on to the actual question of the foundation of morality, and speaks of it only in terms of its origin. The condemnation of morality is therefore based on the uncovering of its origin, according to a line of reasoning that is never made explicit - which is rather surprising, given that it lies at the heart of Nietzsche's condemnation of morality - and that can be summed up as follows: the origin of morality is self-interest, which is a contemptible thing, having a negative value, so morality is a contemptible thing, without value.
This reasoning, obvious on the face of it, is in fact a confusion that we feel cannot be accepted, for a number of reasons.

1. Ibid., §116
2. On the Genealogy of Morals, chap. 1, §10
3. Twilight of the Idols, Maxims and Arrows, 31
4. On the Genealogy of Morals, Prologue, §5
5. The Gay Science, §345