Full Idea
The human essence is no abstraction inherent in each single individual; in its reality it is the ensemble of the social relations.
Gist of Idea
The human essence is not found in individuals but in social relations
Source
Karl Marx (Theses on Feuerbach [1846], §VI)
Book Reference
Marx,K./Engels,F.: 'The German Ideology', ed/tr. Arthur,C.J. [Lawrence and Wishart 1985], p.122
A Reaction
This is a key Marxist doctrine, and the central difference from Aristotle. Personally I am more with Aristotle, but the truth obviously lies somewhere in between. Man must be a 'social being', or there wouldn't be any social relations.