First, what evidence is there that our self-interest in an idea has any bearing on its truth or falsity? There appears to be none. Certainly, we have a vested interest in believing that God exists and that we ought to be moral; that is why such ideas are readily imagined and easily accepted. Nietzsche rightly observes that it would be a mistake to conclude they are true solely because they serve our interests. Yet it would be equally mistaken to conclude that an idea is false because it serves our interests. The fact that we might benefit from God's existence does not imply that he does not exist, just as the fact that moral behaviour aligns with our interests does not imply we should reject it.
Identifying the origin of an idea reveals nothing about its truth or value—its foundation—only about its appeal to us and the importance we attribute to it.

Moreover, the origin of an idea tells us how it came to our attention. Whether we arrived at it through our own weakness or absorbed it from society tells us nothing about its truth or value.

Furthermore, Nietzsche's doctrine rests on an aristocratic axiological assumption that warrants questioning: the idea that something born of a despicable origin can only be despicable in itself. Yet it is common to observe that something arising from humble beginnings can far exceed its original condition in value: a great river springs from a tiny source, a figure as imposing as Napoleon came from a modest Corsican family, Nietzsche himself from a deeply pious household with a pastor for a father, and so forth. Thus, even if morality and the idea of God are born of a petty self-interest, this does not necessarily mean they are themselves petty.

Finally, Nietzsche's condemnation rests on an axiological judgement that appears unfounded and functions as dogma: the assertion that weakness is of lesser value, while power is highly prized. This judgement may be true or false, but it is offered without justification. One can equally conceive of a perspective that affirms the value of gentleness, fragility, and weakness (think of a fawn, a solitary flower in a field, or a child), qualities that often hold a particular appeal for us.

In short, Nietzsche's genealogical study illuminates how moral and religious ideas come to be known, and why they captivate us. His claim to their negative value (or falsity) rests on an unsound inference—from origin to foundation—and on a dogmatic axiological judgement open to challenge from other standpoints. This plurality of perspectives confronts consciousness with the problem of values.

I have sought to show that this approach—ultimately doomed to failure—in attempting to derive the basis of morality from its origin, is not peculiar to Nietzsche. Indeed, a significant number of doctrines, and in particular what we might call 'moral sociologism', appear to follow the same path.

d/ Extension to Moral Sociologism

Moral sociologism may be defined as a doctrine that seeks to justify or critique a particular moral rule by tracing it back to its social cause or conditions. One might praise a given moral rule by showing that it is necessitated by the current state of society—that is, that a deep social cause underlies the establishment of this rule. Conversely (and more frequently), another moral rule might be criticised on the grounds that society has evolved, and that the social cause which originally gave rise to this rule no longer obtains, thus implying that the rule should be abandoned.

It is clear that this doctrine does indeed involve deducing the foundation (or lack thereof) of morality from its origin—specifically, its social origin—since the cause (or condition) of a phenomenon is nothing other than its origin.

Many sociologists would no doubt resist the label of 'moral sociologism'. Nevertheless, it is worth noting that this doctrine was formulated and given conceptual shape by one of the founding figures of sociology, Durkheim, and that it recurs across a wide range of sociological works. I therefore consider it legitimate to speak of 'moral sociologism' as a doctrine that attempts to determine the basis of morality by reference to the social norms prevailing in the society in which that morality is practised.