Karl Marx identified several forms of alienation under capitalism: alienation from the product of labor, the process of labor, one's own human potential (species-essence), and other people. These concepts describe the estrangement of workers from their work and social connections in industrial society.

Karl Marx used the term 'species-being' to describe the true, creative, and social essence of human beings. It represents the potential for humans to engage in free, conscious activity and self-actualization through labor. When humans are alienated from their work under capitalism, they are effectively separated from their species-being, preventing them from realizing their full human potential and authentic connection to the world and others.

Marx argued that alienation is a structural consequence of capitalist production, where workers are separated from the products of their labor, the process of work, and their own human potential. He proposed that communism would resolve this by abolishing private property and the exploitation of the proletariat. By establishing collective ownership, workers would regain control over their labor and social existence, allowing them to achieve their full human potential in a classless society.

Ibn Khaldun, a 14th-century scholar, is often cited for his analysis of social cohesion (asabiyyah) and the cyclical nature of civilizations. Some scholars draw parallels between his focus on material conditions and power dynamics and the later historical materialism developed by Karl Marx, though they operated in vastly different historical contexts.

Historical materialism is a methodological approach developed by Karl Marx. It posits that the material conditions of a society's mode of production fundamentally determine its social structure, culture, and historical development, rather than ideas or consciousness driving change.

Marx defined 'labour power' as the physical and mental capacity of an individual to perform work. He distinguished this from the actual labor performed, noting that in a capitalist system, workers sell their labour power to employers in exchange for a wage.

Marx's labor theory of value posits that the value of a commodity is determined by the labor required to produce it. He argued that capitalists extract 'surplus value' from workers, which constitutes exploitation. Therefore, in his view, the working class (the proletariat) should be the primary beneficiaries of the wealth they create, as they are the ones who perform the actual labor necessary for production.

Karl Marx is the primary theorist associated with this definition. In his analysis of capitalism, he argued that social class is determined by one's position in the economic structure, specifically whether one owns the means of production (the bourgeoisie) or sells their labor power (the proletariat).

Marx challenged Malthusian theories by arguing that poverty and unemployment are not caused by overpopulation or food scarcity, but by the capitalist mode of production. He posited that capitalism requires a 'reserve army of labor' to keep wages low. Therefore, the perceived excess of the working class is a structural feature of the capitalist economy, dependent on the accumulation of capital and the availability of jobs.

The materialist conception of history, primarily developed by Karl Marx, focuses on economic structures, modes of production, and class conflict as drivers of change. 'The spirit of capitalism' is a concept famously associated with Max Weber's work, which emphasizes the role of cultural and religious values rather than purely materialist economic forces in the development of modern capitalism.