Marx asked what divides a society. Émile Durkheim asked what holds one together — and in the course of answering, did something Marx never attempted: he built sociology into a university discipline, with a defined object, a method, a journal, a curriculum and a generation of students.

This lesson is about the concept he put at the foundation of the whole enterprise. Everything else in Topic 4.2 rests on it.

The idea, in plain words

Durkheim's definition, from The Rules:

"A social fact is every way of acting, fixed or not, capable of exercising on the individual an external constraint; or again, every way of acting which is general throughout a given society, while at the same time existing in its own right independent of its individual manifestations."

Unpacked, it has three properties.

"Treat social facts as things"

This is Durkheim's most famous methodological instruction, and the most misread. In French: considérer les faits sociaux comme des choses.

Why society is not reducible to individuals

The argument beneath the whole programme, and Durkheim's answer to "you are just doing psychology." He calls it emergence, or in his own phrase, that society is sui generis — of its own kind.

This is one of the most consequential arguments in the discipline's history. It is the warrant for sociology existing at all (1.4.1), it is inherited from Comte's hierarchy of the sciences (3.3.1), and it remains the central battlefield against methodological individualism (5.3, 7.2). Whether the argument fully works is a live question; that it founded a discipline is not.

Kinds of social fact

Durkheim distinguishes several, and the distinctions matter.

Morphological (or structural) facts — the "anatomical" features of a society: population size and density, geographical distribution, the arrangement of settlements, the channels of communication. These are the most thing-like, and Durkheim gives them causal priority. Dynamic density — the frequency and intensity of interaction among a population — is the key variable in The Division of Labour (4.2.2).

Institutional facts — established, crystallised ways of acting: law, religion, marriage, contract, property, education systems.

Currents of opinion (courants sociaux) — less fixed, more fluid: enthusiasms, panics, waves of feeling. Durkheim's examples include the surge of collective feeling in a crowd, and the rates of suicide, marriage and migration that fluctuate with the moral temper of a society. These are the least thing-like, and the most interesting: they show that a social fact need not be solid to be real.

And "normal" versus "pathological" facts — a distinction that gets him into trouble. Durkheim held that a social fact is normal when it is general in a society of that type at that stage of development, and pathological when it deviates. His most startling application: crime is normal. It occurs in every society; a society without crime is impossible, since if serious offences vanished, minor deviations would attract the same outrage; and crime is even useful, since it provokes the collective reaction that reaffirms shared standards, and since today's crime is sometimes tomorrow's morality — Socrates, he notes, was a criminal.

The trouble is that "normal = general" easily becomes "general = healthy = right," which smuggles a value judgement into what was supposed to be a value-free method. Critics have made this objection since 1895 and it has never been satisfactorily answered.

Go deeper

The three great objections

One: reification. Does Durkheim treat "society" as a real entity with its own existence, above and beyond the people in it — a group mind, a thing that acts and wants? Critics from Gabriel Tarde (his contemporary and most persistent opponent) onward have said yes. Durkheim's defence is that a social fact exists in individual consciousnesses collectively, not in some free-floating spirit; the conscience collective (4.2.5) is a distribution across minds, not a mind of its own. The defence is not always convincing, and some of his own formulations invite the charge.

Two: where is the individual? If social facts determine behaviour, what becomes of choice, resistance, creativity, interpretation? This is the structure/agency problem (1.3.1) in its sharpest form. Durkheim's actual position is more nuanced than his slogans: he insists constraint is not the whole story, that people internalise social facts and experience them as their own obligations rather than as external chains, and that in modern societies individual autonomy is itself a social fact — a collectively produced value, the "cult of the individual" (4.2.5). But the framework tilts heavily towards structure, and Weber's insistence on meaning and interpretation (4.3.1) is the direct counterweight.

Three: too much constraint, not enough conflict. Whose social facts? A rule that feels natural to those it benefits may be experienced as imposition by those it does not. Durkheim tends to write as if a society's moral rules were shared by everyone in it — where Marx would ask whose interests they serve, and Weber would ask which groups fought over them. The conflict tradition's standing criticism of the whole Durkheimian line (5.2) starts here.

The methodological rules

Beyond the definition, The Rules lays out procedures that are still, in modified form, standard.

Define phenomena by external, observable characteristics before investigating them, so that everyday prejudice does not do the work in advance.

Eradicate preconceptions (prénotions) — the ready-made ideas we all carry about family, crime, religion. This is 1.4.6 on common sense, in its founding statement.

Distinguish cause from function. "When we undertake to explain a social phenomenon, we must seek separately the efficient cause which produces it and the function it fulfils." A thing's usefulness does not explain its origin. This is a warning against functionalist over-reach (5.1) issued by the person usually blamed for it — which is worth noticing.

Use the comparative method, and specifically concomitant variation — comparing cases in which a supposed cause is present and absent. Since sociology cannot experiment, comparison is its substitute. Suicide (4.2.4) is the demonstration.

One cause, one effect. If a phenomenon has different causes in different cases, Durkheim argues, it is not one phenomenon but several. This rule is now generally rejected — social outcomes are routinely multiply caused — but it explains why Suicide is structured as it is.

The lasting form of the idea

Where the concept survives today, usually without the name attached.

Institutions as objects. The entire field of new institutionalism — the study of how organisational forms, once established, constrain and shape the people inside them — is Durkheimian in structure. Berger and Luckmann's The Social Construction of Reality (2.4.1) explicitly builds on him: institutions are humanly produced and then experienced as objective reality, a process they call objectivation.

Rates as evidence. Every use of official statistics to reveal something about a society rather than about its individuals rests on Durkheim's argument that a rate is a property of a collective. Every study showing that a country's homicide rate, fertility rate or life expectancy tracks its institutional arrangements is doing what he said sociology should do.

Emergence beyond sociology. The argument that wholes have properties their parts lack is now standard in complexity science, biology and philosophy of mind. Durkheim's version was early, and cruder than modern statements of it, but recognisably the same argument.

And the sharpest modern test: language and technology. A social media platform's affordances are external to any user, constrain what can be done, exist independently of any individual, and shape how millions think and feel. They are also owned by someone, which Durkheim's framework has no easy way to register — and which is exactly where Marx's questions have to be brought back in.

Why it matters

It is sociology's declaration of independence. Without a distinct object of study, sociology is a branch of psychology, history or philosophy. The social fact is that object, and the argument secured the discipline a place in universities that it has not lost.

It gives the "invisible pressure" a name. Lesson 1.1.2 said social structure is hard to see. Durkheim explains why: the strongest social facts are precisely the ones that feel most natural, because we have internalised them so thoroughly that their constraint registers only when we try to break them. The lift experiment is the demonstration.

It legitimates the study of rates. Suicide rates, crime rates, birth rates — treated not as tallies of individual decisions but as properties of a collective, with social causes. This is the foundation of quantitative sociology, and 4.2.4 is the proof of concept.

And it sets up the opposition that organises Part 5. Durkheim's insistence on the primacy of structure and the reality of the collective; Weber's insistence that action must be understood through the meanings actors give it (4.3.1). Almost every theoretical dispute in the twentieth century can be located somewhere between those two positions.