Full Idea
When reality is depicted, philosophy as an independent branch of knowledge loses its medium of existence. At best it is a summing up of general results, abstractions which arise from observation of the historical development of man.
Gist of Idea
Philosophy is no more than abstractions concerning observations of human historical development
Source
K Marx / F Engels (The German Ideology [1846], §1.A)
Book Reference
Marx,K./Engels,F.: 'The German Ideology', ed/tr. Arthur,C.J. [Lawrence and Wishart 1985], p.48
A Reaction
This strikes me as nonsense, based on a bogus Hegelian notion that history is following some sort of pattern, and that mental reality is fixed by physical conditions. The philosophy of mathematics, for one, won't fit into this definition.