Karl Marx, Capital, Volume 1

The labour process, as we have just presented it in its simple and abstract elements, is purposeful activity aimed at the production of use-values. It is an appropriation of what exists in nature for the requirements of man. It is the universal condition for the metabolic interaction between man and nature, the everlasting nature-imposed condition of human existence, and is therefore independent of every form of that existence, or rather it is common to all forms of society in which human beings live. (1:290)

Mode of production: a historically specific combination of (1) productive forces, i.e. human labor-power and means of production (tools, equipment, machines, etc.) (2) relations of production, i.e. the social relations that organize how a society uses its productive forces and how its products are distributed

The history of all hitherto existing society is the history of class struggles. (Karl Marx, Friedrich Engels, “Manifesto of the Communist Party”)

The weapon of critique cannot, of course, replace the critique of the weapon, material force must be overthrown by material force; but theory also becomes a material force as soon as it has gripped the masses. (Marx, Critique of Hegel’s Philosophy of Right)

Socially necessary labour-time is the labor-time required to produce any use-value under the conditions of production normal for a given society and with the average degree of skill and intensity of labour prevalent in that society. (1:129)

The value of a day’s labour-power amounts to 3 shillings, because on our assumption, half a day’s labour is objectified in that quantity of labour-power, i.e. because the means of subsistence required every day for the production of labour-power cost half a day’s labour. But (A) the past labour embodied in the labour-power and (B) the living labour it can perform, and (A) the daily cost of maintaining labour-power and (B) its daily expenditure in work, are two totally different things. The former (i.e. A) determines the exchange value of the labor power (i.e. wages), the latter (i.e. B) is its use-value. The fact that half a day’s labour is necessary to keep the worker alive during 24 hours does not in any way prevent him from working a whole day.

Therefore the value of labour-power, and the value which that labour-power valorizes in the labour-process are two entirely different magnitudes; and this difference was what the capitalist had in mind when he was purchasing labour-power. (…) The owner of the money has paid the value of a day’s labour-power; he therefore has the use of it for a day, a day’s labour belongs to him. On the one hand, the daily sustenance of labour-power costs only half a day’s labour, while on the other hand the very same labour-power can remain effective, can work, during a whole day, and consequently the value which its use during one day creates is double what the capitalist pays for that use; this circumstance is a piece of good luck for the buyer, but by no means an injustice towards the seller. (1:300-301)

M-C-M’ Money - Commodity - Money

In agriculture, as in manufacture, the capitalist transformation of the process of production … appears as a martyrology for the producer; the instrument of labour appears as a means of enslaving, exploiting, and impoverishing the worker; the social combination of labour processes appears as an organized suppression of his individual vitality, freedom, and autonomy. (…) In modern agriculture, as in urban industry, the increase in the productivity and the mobility of labour is purchased at the cost of laying waste and debilitating labour-power itself. Moreover, all progress in capitalist agriculture is a progress in the art, not only of robbing the worker, but of robbing the soil; all progress in increasing the fertility of the soil for a given time is a progress towards ruining the more long-lasting sources of that fertility. The more a country proceeds from large-scale industry as the background of its development, as is the case in the United States, the more rapid is this process of destruction. Capitalist production, therefore, only develops the techniques and the degree of combination of the social process of production by simultaneously undermining the original sources of all wealth — the soil and the worker. (1:638)