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Contribution to the Critique of Hegel's Philosophy of Right, Introduction..., p. 1 (1843).
Context: Religious suffering is, at one and the same time, the expression of real suffering and a protest against real suffering. Religion is the sigh of the oppressed creature, the heart of a heartless world, and the soul of soulless conditions. It is the opium of the people.
The abolition of religion as the illusory happiness of the people is the demand for their real happiness. To call on them to give up their illusions about their condition is to call on them to give up a condition that requires illusions. The criticism of religion is, therefore, in embryo, the criticism of that vale of tears of which religion is the halo.
Criticism has plucked the imaginary flowers on the chain not in order that man shall continue to bear that chain without fantasy or consolation, but so that he shall throw off the chain and pluck the living flower.

Source: The Communist Manifesto

Source: The Communist Manifesto

(1857/58)
Source: MEW Vol. 42, p. 176.
Source: Grundrisse: Foundations of the Critique of Political Economy

Source: Economic & Philosophic Manuscripts of 1844/The Communist Manifesto

Source: The Communist Manifesto

Source: Capital, Vol 1: A Critical Analysis of Capitalist Production

Source: Economic & Philosophic Manuscripts of 1844/The Communist Manifesto

Section 4, paragraph 11 (last paragraph)
Variant translation: Workers of the world, unite!
The Manifesto of the Communist Party (1848)
Variant: The proletarians have nothing to lose but their chains. They have a world to win.
WORKING MEN OF ALL COUNTRIES, UNITE!
Source: The Communist Manifesto
Context: The Communists disdain to conceal their views and aims. They openly declare that their ends can be attained only by the forcible overthrow of all existing social conditions. Let the ruling classes tremble at a Communistic revolution. The proletarians have nothing to lose but their chains. They have a world to win.
WORKING MEN OF ALL COUNTRIES, UNITE!

Marx quoted and translated by Engels (in an 1882 letter to Eduard Bernstein) about the peculiar Marxism which arose in France 1882. Original: &quot;Ce qu&#x27;il y a de certain c&#x27;est que moi, je ne suis pas Marxiste&quot; http://www.marxists.org/archive/marx/works/1882/letters/82_11_02.htm#356 <br class="br">Original: Ce qu&#x27;il y a de certain c&#x27;est que moi, je ne suis pas Marxiste.

Preface to ' (1859).
Source: A Contribution to the Critique of Political Economy
Context: In the social production of their life, men enter into definite relations that are indispensable and independent of their will; these relations of production correspond to a definite stage of development of their material forces of production. The sum total of these relations of production constitutes the economic structure of society — the real foundation, on which rises a legal and political superstructure and to which correspond definite forms of social consciousness. The mode of production of material life determines the social, political and intellectual life process in general. It is not the consciousness of men that determines their being, but, on the contrary, their social being that determines their consciousness. [Es ist nicht das Bewußtsein der Menschen, das ihr Sein, sondern umgekehrt ihr gesellschaftliches Sein, das ihr Bewusstsein bestimmt. ] At a certain stage of their development, the material productive forces in society come in conflict with the existing relations of production, or — what is but a legal expression for the same thing — with the property relations within which they have been at work before. From forms of development of the productive forces these relations turn into fetters. Then begins an epoch of social revolution. With the change of the economic foundation the entire immense superstructure is more or less rapidly transformed. In considering such transformations a distinction should always be made between the material transformation of the economic conditions of production, which can be determined with the precision of natural science, and the legal, political, religious, aesthetic or philosophic — in short, ideological forms in which men become conscious of this conflict and fight it out. Just as our opinion of an individual is not based on what he thinks of himself, so we can not judge of such a period of transformation by its own consciousness; on the contrary, this consciousness must be explained rather from the contradictions of material life, from the existing conflict between the social productive forces and the relations of production. No social order ever disappears before all the productive forces for which there is room in it have been developed; and new, higher relations of production never appear before the material conditions of their existence have matured in the womb of the old society itself. Therefore, mankind always sets itself only such tasks as it can solve; since, looking at the matter more closely, we will always find that the task itself arises only when the material conditions necessary for its solution already exist or are at least in the process of formation. In broad outlines we can designate the Asiatic, the ancient, the feudal, and the modern bourgeois modes of production as so many progressive epochs in the economic formation of society. The bourgeois relations of production are the last antagonistic form of the social process of production — antagonistic not in the sense of individual antagonism, but of one arising from the social conditions of life of the individuals; at the same time the productive forces developing in the womb of bourgeois society create the material conditions for the solution of that antagonism. This social formation constitutes, therefore, the closing chapter of the prehistoric stage of human society.

Source: Contribution to the Critique of Hegel's Philosophy of Right (1843)
Context: It is clear that the arm of criticism cannot replace the criticism of arms. Material force can only be overthrown by material force, but theory itself becomes a material force when it has seized the masses. Theory is capable of seizing the masses when it demonstrates ad hominem, and it demonstrates ad hominem as soon as it becomes radical. To be radical is to grasp things by the root. But for man the root is man himself. What proves beyond doubt the radicalism of German theory, and thus its practical energy, is that it begins from the resolute positive abolition of religion. The criticism of religion ends with the doctrine that man is the supreme being for man. It ends, therefore, with the categorical imperative to overthrow all those conditions in which man is an abased, enslaved, abandoned, contemptible being—conditions which can hardly be better described than in the exclamation of a Frenchman on the occasion of a proposed tax upon dogs: 'Wretched dogs! They want to treat you like men!

Letter from Marx to Arnold Ruge (September 1843)

This has been compared to Horace Walpole's statement: "This world is a comedy to those that think, a tragedy to those that feel."
Variant translation: Hegel remarks somewhere that all facts and personages of great importance in world history occur, as it were, twice. He forgot to add: the first time as a tragedy, the second time as farce.
Source: The Eighteenth Brumaire of Louis Bonaparte (1852)

Attributed to Karl Marx, a composer with the same name.
Misattributed

Comments on the North American Events (1862)
Context: Lincoln is not the product of a popular revolution. This plebeian, who worked his way up from stone-breaker to Senator in Illinois, without intellectual brilliance, without a particularly outstanding character, without exceptional importance-an average person of good will, was placed at the top by the interplay of the forces of universal suffrage unaware of the great issues at stake. The new world has never achieved a greater triumph than by this demonstration that, given its political and social organisation, ordinary people of good will can accomplish feats which only heroes could accomplish in the old world!

Remarks against personality cults from a letter to W. Blos (10 November 1877).
Context: Neither of us cares a straw for popularity. A proof of this is for example, that, because of aversion to any personality cult, I have never permitted the numerous expressions of appreciation from various countries with which I was pestered during the existence of the International to reach the realm of publicity, and have never answered them, except occasionally by a rebuke. When Engels and I first joined the secret Communist Society we made it a condition that everything tending to encourage superstitious belief in authority was to be removed from the statutes.

The German Ideology (1845/46)
Context: The fact is, therefore, that definite individuals who are productively active in a definite way enter into these definite social and political relations. Empirical observation must in each separate instance bring out empirically, and without any mystification and speculation, the connection of the social and political structure with production. The social structure and the state are continually evolving out of the life-process of definite individuals, but of individuals, not as they appear in their own or other people's imagination, but as they really are; i. e. as they are effective, produce materially, and are active under definite material limits, presuppositions and conditions independent of their will.
The production of ideas, of conceptions, of consciousness, is at first directly interwoven with the material activity and the material intercourse of men, the language of real life. Conceiving, thinking, the mental intercourse of men, appear at this stage as the direct efflux of their material behaviour. The same applies to mental production as expressed in the language of the politics, laws, morality, religion, metaphysics of a people. Men are the producers of their conception, ideas, etc. — real, active men, as they are conditioned by a definite development of their productive forces and of the intercourse corresponding to these, up to its furthest forms. Consciousness can never be anything else than conscious existence, and the existence of men is their actual life-process. If in all ideology men and their circumstances appear upside down as in a camera obscura, this phenomenon arises just as much from their historical life-process as the inversion of objects on the retina does from their physical life-process.