Initially, Durkheim appears to rule out any attempt to justify or invalidate morality, even within a society. In Sociology and Philosophy, he cautiously states: Moral reality, like all reality, can be studied from two different points of view. One can seek to know and understand it; or one can propose to judge it. The first of these problems, which is theoretical, must necessarily precede the second, and it is the only one that will be dealt with here ¹.

The aim here, then, is to understand morality, not to judge it; however, Durkheim subtly shifts from one perspective to the other, as we will observe.

Durkheim's primary objective was to demonstrate that a moral fact constitutes a social fact. To do this, he relies on the idea that an act can never be called moral if its sole object is the interest of the individual or of other individuals. Morality can only have as its objective the group formed by a plurality of associated individuals, i.e. society, understood as a personality that is qualitatively different from the individual personalities that make it up. As a result, Morality begins where attachment to any group begins ².

Above all, a moral fact is a social fact because it corresponds perfectly to Durkheim's definition of a social fact in the Rules of Sociological Method. In this work, Durkheim aimed to establish sociology as an autonomous discipline, distinct and irreducible to the fields to which it had often been reduced, such as psychology and biology.

At the time, the prevailing belief was that, since society consisted of individuals, social rules originated from individual minds, making it possible to base sociology on psychological analysis and thus deprive it of independent standing in favour of psychology.
Similarly, society was often thought to be analogous to a biological organism, with individuals likened to the cells of that organism. This biological metaphor led to sociology being deprived of any distinct consistency, with its content and methods assumed to align with those of biology.

Durkheim counters this perspective by demonstrating that a social fact has its own distinct definition, separate from biologistic or psychologising interpretations. He argues that even when individuals conform to social rules, aligning their personal beliefs with these norms, the rules themselves do not originate from the individual mind (i.e., they are not psychological); rather, they are externally imposed, independent of individual preference. These rules exist before us and outside us, and are endowed with an imperative and coercive power by virtue of which [they] impose themselves on us whether we like it or not. They cannot therefore be derived from my mind, but are imposed on it, which is why sociology does not derive from psychology.

This leads Durkheim to conclude that a fact is social because it is obligatory: A social fact is recognisable by the power of external coercion which it exercises or is likely to exercise over individuals; and the presence of this power is in turn recognisable by the existence of some specific sanction or by the resistance which the fact opposes to any individual undertaking which tends to do it violence ³.

A moral fact is, therefore, essentially a social fact, placing it within the realm of sociology due to its obligatory nature. The next question is whether sociology, as the science of social facts, can provide a foundation for morality as a social fact. In other words, does sociology offer a solution to the problem of establishing a foundation for morality?
Durkheim's response to this question is affirmative: one moral rule will be justified if social causes have supported its development and continuity; another will be discarded if the social conditions that prompted its adoption no longer exist, rendering it a groundless remnant of a bygone social state:
The awareness that society acquires of itself in and through opinion may be inadequate to the underlying reality. It may be that opinion is full of survivals, lagging behind the real state of society [or that] certain principles of existing morality are, for a time, rejected in the unconscious. Fortunately, the science of morality makes it possible to rectify these errors ⁴.

From this approach to grounding specific moral rules, Durkheim derives a basis for morality as a whole: It will be maintained that no morality can ever be desired other than that which is demanded by the social state of the time. To desire a morality other than that which is inherent in the nature of society is to reject it, and, consequently, to reject oneself ⁵.

1. Sociology and philosophy, chap. II
2. Ibid.
3. Rules of sociological method, chap. I
4. Sociology and philosophy, chap. II
5. Ibid.