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.

V. Lenin