Das Kapital ("Capital") is a very large treatise of political economy written by Karl Marx. The book is a critical analysis of capitalism, its economic practices and the theories which economists made about it. As noted by S. S. Prawer in "Karl Marx and World Literature" (1978), it has not only scientific but also important literary merits.
Marx bases his work on that of the classical economists like Adam Smith, David Ricardo, and even Benjamin Franklin. However, he reworks these authors' ideas critically and carefully, so his book is a critical and very innovative synthesis that does not follow the lead of any one thinker. It also reflects the dialectical methodology applied by G.W.F. Hegel in his books The Science of Logic and The Phenomenology of Mind, and the influence of French socialists such as Charles Fourier, Comte de Saint-Simon and Pierre-Joseph Proudhon.
Marx said himself that his aim was "to bring a science [i.e. political economy] by criticism to the point where it can be dialectically represented", and in this way to "reveal the law of motion of modern society". By showing how capitalist development was the precursor of a new, socialist mode of production, he aimed to provide a scientific foundation for the modern labor movement. In preparation for his book, he studied the economic literature available in his time for a period of twelve years, mainly in the British Museum in London.
The central injustice of capitalism, according to Marx, was in the exploitation and alienation of labor, a condition which a later Marxist commentator, Harry Braverman , called "the degradation of labor". The ultimate source of the new profits and value-added was that employers paid workers the market value of their labor-capacity, but the value of the commodities workers produced exceeded that market value. Employers were entitled to appropriate the new output value because of their ownership of the productive capital assets. By producing output as capital for the employers, the workers constantly reproduced the condition of capitalism by their labor.
However, though Marx is very concerned with the social aspects of commerce, his book is not an ethical treatise, but an (unfinished) attempt to explain the objective "laws of motion" of the capitalist system as a whole, its origins and future. He aims to reveal the causes and dynamics of the accumulation of capital, the growth of wage labor, the transformation of the workplace, the concentration of capital, competition, the banking and credit system, the tendency of the rate of profit to decline, land-rents and many other things.
Marx viewed the commodity as the "cell-form" or building unit of capitalist society - it is an object useful to somebody else, but with a trading value for the owner. Because commercial transactions imply no particular morality beyond what is required to settle transactions, the growth of markets cause the economic sphere and the moral-legal sphere to become separated in society: subjective moral value becomes separated from objective economic value. Political economy, which was originally thought of as a "moral science" concerned with the just distibution of wealth, gave way to separate disciplines of economic science, law and ethics.
Marx believed the political economists could study the scientific laws of capitalism in an "objective" way, because the expansion of markets had in reality objectified most economic relations: the cash nexus stripped away all previous illusions. Marx also says that he viewed "the economic formation of society as a process of natural history". The growth of commerce happened as a process which no individuals could control or direct, creating an enormously complex web of social interconnections globally. Thus a "society" was formed "economically" before people actually began to consciously master the enormous productive capacity and interconnections they had created, in order to put it collectively to the best use.
Marx published the first volume of Das Kapital in 1867, but he died before he could finish the second and third ones which he had already drafted; these were edited by his friend and collaborator Friedrich Engels and published in 1885 and 1894; the fourth volume, called Theories of Surplus-Value, was first edited and published by Karl Kautsky in 1905-1910.
Other preparatory manuscripts were published only decades later.
Marx notes in his preface to the French edition of Das Kapital that the beginning of his work might not be easy reading (since he defines many terms), but after that the book becomes easier to read. Many readers agree that the very beginning of Das Kapital is the most difficult and obscure part, discouraging potential readers. There exist nowadays a very large number of commentaries, popularisations and vulgarisations of Marx's Das Kapital but for the interested reader the best advice is to begin with the famous book itself. Many socialists say that they found reading the book in a discussion group most satisfying.