linguistic:paraphrasing
Critique of political economy, history and society

But you Communists would introduce community of women, screams the whole bourgeoisie in chorus. The bourgeois sees in his wife a mere instrument of production. He hears that the means of production are to be exploited in common, and, naturally, can come to no other conclusion than that the lot of being common to all will likewise fall to the women. He has not even a suspicion that the real point aimed at is to do away with the status of women as mere mean of production.

—Karl Marx, The Communist Manifesto

Marx's thoughts on labour and its function in reproducing capital were related to the primacy he gave to social relations in determining the society's past, present and future. (Critics have called this economic determinism.) Labour is the precondition for the existence of, and accumulation of capital, which both shape the social system. For Marx, social change was driven by conflict between opposing interests, by parties situated in the historical situation of their mode of production. This became the inspiration for the body of works known as the conflict theory. In his evolutionary model of history, he argued that human history began with free, productive and creative activities that was over time coerced and dehumanised, a trend most apparent under capitalism. Marx noted that this was not an intentional process, but rather due to the immanent logic of the current mode of production which demands more human labour (abstract labour) to reproduce the social relationships of capital.

The organisation of society depends on means of production. The means of production are all things required to produce material goods, such as land, natural resources, and technology but not human labour. The relations of production are the social relationships people enter into as they acquire and use the means of production. Together, these compose the mode of production and Marx distinguished historical eras in terms of modes of production. Marx differentiated between base and superstructure, where the base (or substructure) is the economic system and superstructure is the cultural and political system. Marx regarded this mismatch between economic base and social superstructure as a major source of social disruption and conflict.

Despite Marx's stress on the critique of capitalism and discussion of the new communist society that should replace it, his explicit critique is guarded, as he saw it as an improved society compared to the past ones (slavery and feudalism). Marx never clearly discusses issues of morality and justice, but scholars agree that his work contained implicit discussion of those concepts.

Marx's view of capitalism was two-sided. On one hand, in the 19th century's deepest critique of the dehumanising aspects of this system he noted that defining features of capitalism include alienation, exploitation and recurring, cyclical depressions leading to mass unemployment. On the other hand, he characterised capitalism as "revolutionising, industrialising and universalising qualities of development, growth and progressivity" (by which Marx meant industrialisation, urbanisation, technological progress, increased productivity and growth, rationality, and scientific revolution) that are responsible for progress, at in contrast to earlier forms of societies. Marx considered the capitalist class to be one of the most revolutionary in history because it constantly improved the means of production, more so than any other class in history and was responsible for the overthrow of feudalism. Capitalism can stimulate considerable growth because the capitalist has an incentive to reinvest profits in new technologies and capital equipment.

According to Marx, capitalists take advantage of the difference between the labour market and the market for whatever commodity the capitalist can produce. Marx observed that in practically every successful industry, input unit-costs are lower than output unit-prices. Marx called the difference " surplus value " and argued that it was based on surplus labour, the difference between what it costs to keep workers alive, and what they can produce. Although Marx describes capitalists as vampires sucking worker's blood, he notes that drawing profit is "by no means an injustice" since Marx, according to Allen W. Wood "excludes any trans-epochal standpoint from which one can comment" on the morals of such particular arrangements. Marx also noted that even the capitalists themselves cannot go against the system. The problem is the "cancerous cell" of capital, understood not as property or equipment, but the social relations between workers and owners, (the selling and purchasing of labour power) – the societal system, or rather mode of production, in general.

At the same time, Marx stressed that capitalism was unstable and prone to periodic crises. He suggested that over time capitalists would invest more and more in new technologies and less and less in labour. Since Marx believed that profit derived from surplus value appropriated from labour, he concluded that the rate of profit would fall as the economy grows. Marx believed that increasingly severe crises would punctuate this cycle of growth and collapse. Moreover, he believed that in the long-term, this process would enrich and empower the capitalist class and impoverish the proletariat. In section one of The Communist Manifesto, Marx describes feudalism, capitalism and the role internal social contradictions play in the historical process:

We see then: the means of production and of exchange, on whose foundation the bourgeoisie built itself up, were generated in feudal society. At a certain stage in the development of these means of production and of exchange, the conditions under which feudal society produced and exchanged... the feudal relations of property became no longer compatible with the already developed productive forces; they became so many fetters. They had to be burst asunder; they were burst asunder. Into their place stepped free competition, accompanied by a social and political constitution adapted in it, and the economic and political sway of the bourgeois class. A similar movement is going on before our own eyes... The productive forces at the disposal of society no longer tend to further the development of the conditions of bourgeois property; on the contrary, they have become too powerful for these conditions, by which they are fettered, and so soon as they overcome these fetters, they bring order into the whole of bourgeois society, endanger the existence of bourgeois property.

Marx believed that those structural contradictions within capitalism necessitate its end, giving way to socialism, or a post-capitalistic, communist society:

The development of modern industry, therefore, cuts from under its feet the very foundation on which the bourgeoisie produces and appropriates products. What the bourgeoisie, therefore, produces, above all, are its own grave-diggers. Its fall and the victory of the proletariat are equally inevitable.

Thanks to various processes overseen by capitalism, such as urbanisation, the working class, the proletariat, should grow in numbers and develop class consciousness, in time realising that they can and must change the system. Marx believed that if the proletariat were to seize the means of production, they would encourage social relations that would benefit everyone equally, abolishing the exploiting class and introducing a system of production less vulnerable to cyclical crises. Marx argued in The German Ideology that capitalism will end through the organised actions of an international working class:

Communism is for us not a state of affairs which is to be established, an ideal to which reality will have to adjust itself. We call communism the real movement which abolishes the present state of things. The conditions of this movement result from the premises now in existence.

In this new society, the alienation would end and humans would be free to act without being bound by selling their labour. It would be a democratic society, enfranchising the entire population. In such a utopian world, there would also be little need for a state, whose goal was previously to enforce the alienation. Marx theorised that between capitalism and the establishment of a socialist/communist system, would exist a period of dictatorship of the proletariat – where the working class holds political power and forcibly socialises the means of production. As he wrote in his Critique of the Gotha Program, "between capitalist and communist society there lies the period of the revolutionary transformation of the one into the other. Corresponding to this is also a political transition period in which the state can be nothing but the revolutionary dictatorship of the proletariat". While he allowed for the possibility of peaceful transition in some countries with strong democratic institutional structures (such as Britain, the United States, and the Netherlands), he suggested that in other countries in which workers cannot "attain their goal by peaceful means" the "lever of our revolution must be force".