The task of a bourgeois professor is not to lay bare the entire mechanism, or to expose all the machinations of the bank monopolists, but rather to present them in a favourable light.

Vladimir Lenin
Imperialism: the Highest Stage of Capitalism

Certain bourgeois writers (now joined by Karl Kautsky, who has completely abandoned the Marxist position he had held, for example, in 1909) have expressed the opinion that international cartels, being one of the most striking expressions of the internationalisation of capital, give the hope of peace among nations under capitalism. Theoretically, this opinion is absolutely absurd, while in practice it is sophistry and a dishonest defence of the worst opportunism.

Vladimir Ilyich Lenin
Imperialism, the Highest Stage of Capitalism

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.

Karl Marx
Critique of the Gotha Programme

The economic oppression of the workers inevitably calls forth and engenders every kind of political oppression and social humiliation, the coarsening and darkening of the spiritual and moral life of the masses. The workers may secure a greater or lesser degree of political liberty to fight for their economic emancipation, but no amount of liberty will rid them of poverty, unemployment, and oppression until the power of capital is overthrown. Religion is one of the forms of spiritual oppression which everywhere weighs down heavily upon the masses of the people, over burdened by their perpetual work for others, by want and isolation. Impotence of the exploited classes in their struggle against the exploiters just as inevitably gives rise to the belief in a better life after death as impotence of the savage in his battle with nature gives rise to belief in gods, devils, miracles, and the like. Those who toil and live in want all their lives are taught by religion to be submissive and patient while here on earth, and to take comfort in the hope of a heavenly reward. But those who live by the labour of others are taught by religion to practise charity while on earth, thus offering them a very cheap way of justifying their entire existence as exploiters and selling them at a moderate price tickets to well-being in heaven. Religion is opium for the people. Religion is a sort of spiritual booze, in which the slaves of capital drown their human image, their demand for a life more or less worthy of man.

But a slave who has become conscious of his slavery and has risen to struggle for his emancipation has already half ceased to be a slave. The modern class-conscious worker, reared by large-scale factory industry and enlightened by urban life, contemptuously casts aside religious prejudices, leaves heaven to the priests and bourgeois bigots, and tries to win a better life for himself here on earth. The proletariat of today takes the side of socialism, which enlists science in the battle against the fog of religion, and frees the workers from their belief in life after death by welding them together to fight in the present for a better life on earth.

V. I. Lenin
Socialism and Religion

With the clarity and brilliance of genius, this work outlines a new world-conception, consistent materialism, which also embraces the realm of social life; dialectics, as the most comprehensive and profound doctrine of development; the theory of the class struggle and of the world-historic revolutionary role of the proletariat—the creator of a new, communist society.

Vladimir Lenin on the Manifesto, 1914

In bourgeois society, therefore, the past dominates the present; in Communist society, the present dominates the past. In bourgeois society capital is independent and has individuality, while the living person is dependent and has no individuality.

Marx & Engels, Communist Manifesto (1848)

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 communist revolution.
The proletarians have nothing to lose but their chains. They have a world to win.
Working Men of All Countries, Unite!

Marx & Engels, Communist Manifesto (1848)