Karl Marx, answered from the texts and cited to the page.
The relations of production are the definite social relations that human beings enter into in the course of producing their material life — not chosen freely, but determined by the stage of development of the material productive forces. They are the form that production takes at a given historical moment: who owns the instruments of production, who commands the labor, who appropriates the product.
The first thing to clear away is the bourgeois economist's trick of dissolving these historically specific relations into eternal natural categories. Capital is, among other things, an instrument of production, also objectified past labour — and from this the apologist concludes that capital is therefore a general, eternal relation of nature.1
But this inference works only by leaving out precisely the specific quality that makes an instrument of production into capital — namely, the social relation under which stored-up labour confronts living labour as an alien, dominating power. Strip that out and you have saved the abstraction by losing the whole content. Production in general is a rational abstraction, useful insofar as it fixes what is genuinely common across epochs; but the common element itself splits into different determinations, some belonging to all epochs, others only to a few.2
The error is to stop at the abstraction and forget the essential differences — to smudge all historical distinctions and see bourgeois relations in all forms of society.3 One can understand tithe and tribute once one knows ground rent, but one must not identify them. The relations of production correspond to a definite stage of development of the material productive forces.
From forms of development of those forces, these relations turn into their fetters — and then an epoch of social revolution commences.4 Friedrich Engels and I saw this movement in the history of bourgeois society itself: the feudal property relations that once advanced production began impeding it, became so many fetters, and had to be sprung open.5
The same movement is now visible in the contradictions of bourgeois production — the periodic commercial crises, the epidemic of overproduction, the revolt of modern productive forces against the very property relations that called them into existence.6 The relations of production, then, are not a legal or philosophical category imposed from outside on an otherwise neutral technical process. They are the social form that production itself takes — and their transformation is the hinge on which history turns.
Capital is, among other things, also an instrument of production, also objectified, past labour. Therefore capital is a general, eternal relation of nature; that is, if I leave out just the specific quality which alone makes 'instrument of production' and 'stored-up labour' into capital.Grundrisse, pp. 18–19
Production in general is an abstraction, but a rational abstraction in so far as it really brings out and fixes the common element and thus saves us repetition. Still, this general category, this common element sifted out by comparison, is itself segmented many times over and splits into different determinations. Some determinations belong to all epochs, others only to a few.Grundrisse, pp. 18–19
One can understand tribute, tithe, etc., if one is acquainted with ground rent. But one must not identify them.Grundrisse, p. 38
From forms of development of the productive forces these relations turn into their fetters. Then an epoch of social revolution commences.Preface’ to A Contribution to the Critique of Political Economy, pp. 160–161
the relations in which feudal society produced and exchanged, the feudal organisation of agriculture and small-scale manufacture, in a word feudal property relations, no longer corresponded to the forces of production already developed. They impeded production instead of advancing it. They became just so many fetters. They had to be sprung open, they were sprung open.Manifesto of the Communist Party (with Friedrich Engels), pp. 6–7
The forces of production available to society no longer serve for the advancement of bourgeois civilisation and the bourgeois relations of production.Manifesto of the Communist Party (with Friedrich Engels), pp. 6–7