The more the worker exerts himself, the more powerful becomes the alien objective world which he fashions against himself, the poorer he and his inner world become, the less there is that belongs to him. It is the same in religion. The more man attributes to God, the less he retains in himself. The worker puts his life into the object … the externalization of the worker in his product means not only that his work becomes an object, an external existence, but also that it exists outside him, independently, alien, an autonomous power, opposed to him. The life he has given to the object confronts him as hostile and alien.
Karl Marx. Economic and Philosophical Manuscripts of 1844. 78-79.