We have the framework (4.1.1) and its machinery (4.1.2). Now the thing that moves inside it.
The Communist Manifesto opens, after the famous line about a spectre haunting Europe, with a claim so large it is easy to skim past: "The history of all hitherto existing society is the history of class struggles."
This lesson asks what a class actually is in Marx's sense — which is not what most people mean by the word — and what that sentence is really claiming.
The idea, in plain words
In capitalism, Marx's two principal classes:
The bourgeoisie — owners of the means of production, who buy labour power and live from the surplus it generates.
The proletariat — those who own no means of production and must sell their labour power to live.
Note the definition of the proletariat carefully: it is not "poor people," and it is not "manual workers." It is people who have no way of living except by selling their capacity to work. A software engineer on a large salary is, on this definition, a proletarian. This sounds absurd until you ask what happens to that engineer when the company restructures, and notice that the answer is categorically different from what happens to the person who owns the company.
Marx's other classes
The two-class model is Marx's analytical skeleton, not his description of any actual society. His historical writing is populated.
The petty bourgeoisie — small proprietors who own means of production but work them themselves: shopkeepers, artisans, small farmers, the self-employed. Marx expected them to be crushed between the two main classes and largely proletarianised. This has partly happened and partly not; the self-employed sector in most rich countries is stubbornly persistent, and gig platforms have created a large category of workers who are formally petty bourgeois — owning their vehicle, bearing their own costs, legally independent — while being economically dependent in the manner of employees. Marx would have found this arrangement extremely interesting.
The landed aristocracy — owners of land drawing rent, a residual class from the previous mode of production, allied and in conflict with industrial capital by turns. Much of nineteenth-century British politics, including the Corn Law fight, is legible as a quarrel between landed and industrial property.
The lumpenproletariat — Marx's contemptuous term for those outside regular production: vagrants, criminals, the chronically destitute. He regarded them as politically unreliable and available for hire by reaction. This is the least defensible part of his class analysis — moralistic, empirically thin, and the ancestor of a great deal of unpleasant talk about an "underclass." Modern sociology of poverty (8.6) has demolished the notion of a distinct population permanently outside the labour force; movement in and out of insecure work is the norm.
The peasantry — a class by structural position, but one Marx thought incapable of acting as a class. His image in The Eighteenth Brumaire is famous: French smallholding peasants are like potatoes in a sack, "formed by the simple addition of homologous magnitudes" — similar to one another but not connected to one another, and therefore "incapable of enforcing their class interest in their own name." Twentieth-century history in Russia, China, Vietnam and Mexico was rather rough on this judgement.
What class struggle actually claims
Back to the Manifesto's opening. Engels added a footnote in 1888 restricting it to "all written history," in deference to the anthropology of the time — an early sign that the claim was felt to need qualification.
Read carefully, the claim has three parts, of quite different strength.
One: every society since the emergence of a surplus has been divided into classes with opposed interests over the disposal of that surplus. This is strong and largely defensible. Freeman and slave, patrician and plebeian, lord and serf, guild-master and journeyman — Marx's own list.
Two: the conflict between these classes is the principal motor of large-scale historical change. This is contestable, and contested. Marx's own historical writing gives real causal weight to states, wars, religion and contingency. Weber's counter-case is that status groups, parties, bureaucracies and religious ideas are independent forces (4.3.6, 4.3.7). The honest position is that class conflict is one major motor, demonstrably so, and that claiming it is the motor requires ignoring or reducing a great deal.
Three: the conflict is structural, not personal. This one is essential and frequently missed. Marx is not saying capitalists are bad people. He says so explicitly in the preface to Capital: he deals with individuals "only in so far as they are the personifications of economic categories, embodiments of particular class-relations and class-interests," and "my standpoint... can less than any other make the individual responsible for relations whose creature he socially remains."
A kind employer who pays above the market rate, provides good conditions and knows his workers' names is still occupying a position defined by the extraction of surplus — and is under competitive pressure from employers who do none of those things. The analysis is about positions and pressures, not about virtue. This is precisely what makes it sociology rather than moralising (1.1.1).
Go deeper
Did Marx get the trajectory wrong?
He made several predictions about class structure, and it is worth grading them honestly rather than defending or dismissing wholesale.
Polarisation into two classes. Partly wrong. The twentieth century produced an enormous stratum of professionals, managers, technicians and public employees who fit neither pole comfortably. Erik Olin Wright built a career on this, developing the concept of contradictory class locations: managers, for instance, are employees who nonetheless exercise authority over other employees and act for capital. That is not a fudge; it is an attempt to keep a relational framework while acknowledging what actually exists.
Immiseration — the claim that workers' conditions would worsen absolutely. Wrong for the rich countries over the long run. Real wages in the industrialised world rose substantially from the late nineteenth century onwards. Whether they rose because of capitalism or because of organised labour, suffrage and state regulation wrung concessions from it is a live argument — but the absolute claim failed. A weaker version, relative immiseration (the workers' share of a growing product falling), has more support: the labour share of national income has declined in most rich countries since around 1980, and top income shares have risen towards early-twentieth-century levels.
Disappearance of the petty bourgeoisie. Partly wrong, as noted.
Proletarian revolution in the most advanced capitalist countries. Wrong. Revolutions claiming his name occurred in Russia and China — agrarian societies where his own theory said they should not. This is the largest single failure of prediction in the framework, and it deserves to be stated plainly.
Concentration of capital. Right, strikingly. Firms grew, merged and dominated exactly as he expected. The scale of contemporary corporate concentration would not have surprised him at all.
The globalisation of capitalist relations. Right, and early. The Manifesto's passage on the bourgeoisie chasing over the whole surface of the globe, nestling everywhere, settling everywhere, establishing connections everywhere — written in 1848 — is quoted approvingly by people who agree with nothing else he wrote.
What class does and does not predict now
The honest state of the evidence, which is neither "class is dead" nor "class explains everything."
Class position, however measured, remains among the strongest predictors of: life expectancy and healthy life expectancy; child mortality; educational attainment; exposure to occupational injury; job security in downturns; wealth (far more unequal than income); and — importantly — the wealth and class position of one's children.
Class has weakened as a predictor of: party vote in many countries, where education, age, region and cultural identity now do more work; self-identification, which in surveys tends to bunch enormously in the middle; and immediate consumption patterns, which are cheaper to imitate than they were.
And Marx's specific definition competes with others. Weber (4.3.6) splits the field into class (market situation), status (social honour) and party (organised power) — three dimensions rather than one, and better at explaining why Mr Harrow despises Mrs Kelly. Bourdieu (5.10) adds cultural and social capital, showing how taste and comportment transmit advantage. Erik Olin Wright attempted a synthesis, defining classes by ownership, authority and scarce skills together. Goldthorpe's schema, used across European official statistics, classifies by employment relations — the terms of the employment contract, not ownership.
Note that every one of these is arguing with Marx, and every one retains the core relational insight: class is about how you stand in relation to other people in the productive order, not about a number.
And the largest omission
Marx's class analysis has a systematic blind spot that his successors had to repair.
Gender. The wage labourer's ability to appear at work depends on someone having fed him, washed his clothes, raised his replacements and cared for him when sick. That labour was and largely remains unpaid, and it was and largely remains women's. Marx knew domestic labour existed and had almost nothing analytic to say about it. The domestic labour debate of the 1970s and the social reproduction theory that grew from it (8.5) are the repair.
Race. Slavery, indenture and colonial forced labour were not archaic survivals awaiting absorption into free wage labour; they were constitutive of the capitalism Marx analysed, and he substantially underweighted them. Marx did see part of this — his line that "labour in the white skin can never emancipate itself where it is branded in the black skin" is a genuine recognition — and he supported the Union in the American Civil War and the abolition of slavery unequivocally. But the systematic analysis came later: Du Bois (4.5), Oliver Cox, Cedric Robinson's racial capitalism, and the split labour market literature (8.4).
Why it matters
It gives inequality a mechanism instead of a description. Stratification research can tell you the distribution; class analysis proposes why it takes that shape and what reproduces it. You need not accept the answer to see the value of demanding one.
It explains why conflict persists through personnel changes. Structural opposition survives the replacement of individuals. This is the same lesson as 1.1.1, applied to the economy: stop looking at character, look at position.
It underlies the largest arguments in the discipline. Weber's three dimensions, Bourdieu's capitals, Wright's contradictory locations, Goldthorpe's employment relations, intersectionality's insistence on class with race and gender (8.7) — all of it is a conversation begun here.
And it names the mechanism the rest of Topic 4.1 will specify. We have said the owner takes a surplus. We have not yet said how, given that the worker is paid and free and the transaction looks fair. That is 4.1.5, and getting there requires first understanding what the arrangement does to the person inside it — which is 4.1.4.