The worker (lit. labourer) feels to be himself outside work and feels outside himself when working. He is at home when he does not work. When he works, he is not at home. As a result, his work is forced labour, not voluntary labour. Forced labour is not the satisfaction of a need but only a means for satisfying needs outside labour. Its foreignness appears in that labour is avoided as a plague as soon as no physical or other force exists.

Karl Marx, Economic-Philosophical Manuscripts, 1844