It was during the 19th century that the critique of capitalism, particularly the Marxist critique, emerged.

What good is the right to speak, write, and vote, Marx exclaimed, if daily life is a struggle for survival? Beyond a certain threshold, poverty equates to a state of servitude. The social order thus benefits everyone only if the principle of a fair distribution of goods is applied. It was this critique of liberalism that led Marx to consider the necessity of a rational and planned control of the social order. Henceforth, the minimal state of the liberals must be succeeded by a strong state capable of establishing real equality, which, according to Marx, goes as far as the abolition of private property and its collectivization. In a more softened version, "social democracy," the state is asked to guarantee not only the abstract rights of man but the concrete rights of man. New rights are created, social and economic rights, guaranteed by the state: the right to work, the right to housing, the right to health (free), the right to education (free).

The fundamental critique that Marx makes of political liberalism, particularly in his early writings (Critique of Hegel's Philosophy of Right and On the Jewish Question), focuses on the separation of civil society and the state. This critique must be understood within the general framework of his interpretation of the "Bourgeois Revolution." It is this revolution that leads to the formation of a state separated from civil society, which is supposed to aim for the universal, meaning the common interest, by playing the role of an impartial arbitrator.

However, all of this is, for Marx, merely a deceptive appearance. In reality, the state is nothing but an instrument intended to serve the particular interests of the ruling class. In other words, the state is not impartial; it is not separated from civil society. In fact, the liberal state is the site of a double illusion. The illusion of the universal, as we have just seen, and consequently, the illusion of emancipation. Indeed, the Revolution emancipated the citizen by instituting popular sovereignty and equality before the law, but this freedom and equality remain purely ideal and abstract. It is false, Marx says, to think, like Rousseau or Hegel, that man fully realizes his rational nature by becoming a citizen. In reality, one can become a citizen and remain exploited, enslaved, abandoned to the whims of desires, to the anarchy of selfishness, and the law of the strongest.

The emancipation of the citizen, according to Marx, does not at all signify the emancipation of man, as the Declaration of 1789 suggests, but rather the triumph of destructive individualism and therefore of inequality. Freedom, as the power to do anything that does not harm others, a pillar of human rights, is a purely negative freedom that does not establish a relationship between individuals but, on the contrary, promotes their separation, antagonism, and ultimately their servitude. The freedom of human rights is formal.

This political illusion of liberalism is the secular side of the religious illusion, Marx adds. The formula is well-known: "religion is the opium of the people." Religion is a source of consolation, offering euphoria and promising emancipation in the afterlife. But it diverts man from his true emancipation here on earth. Citizenship is, in relation to the activity of the worker, like the kingdom of God regarding miserable existence on this earth. It is never realized. This double separation constitutes a double alienation, meaning the non-fulfillment by man of his humanity or his imaginary accomplishment.

In fact, according to Marx and historical materialism, economic alienation is at the root of both political and religious alienation. In economic alienation, a result of capitalism (defined as the private ownership of the means of production), the worker is compelled to sell their labor power as a commodity. Moreover, he is deprived of the product of his labor, which the employer owns. He is thus alienated, meaning separated from himself, because his work becomes something foreign to him that he performs out of necessity to survive. Yet, work, for Marx, is the quintessentially human act, the one through which the very essence of man, namely freedom, is realized. This is why the liberation of labor also means restoring humanity to man.

Political revolution is, therefore, an illusion, according to him, as long as it is not accompanied by an economic and social revolution capable of freeing man from capitalist servitude and thus achieving unity between the worker and the citizen, between society and the state, the private sphere and the public sphere. The formal freedom and equality of citizens will thus become a reality in a classless society.