Das Kapital sciences published before 1950. In "Das Kapital" (1867), Marx proposes that the motivating force of capitalism is in the exploitation of labor, whose unpaid work is the ultimate source of surplus value. The owner of the means of production is able to claim the right to this surplus value because he or she is legally protected by the ruling regime through property rights and the legally established distribution of shares which are by law only to be distributed to company owners and their board members. The historical section shows how these rights were acquired in the first place chiefly through
Biographies of Karl Marx (1925), Japanese (1930), Spanish (1932), and English (1935). Marx: Man and Fighter is a biography by Boris Nicolaievsky, first published in German in 1933. It was translated into English by Otto Mänchen-Helfen and published in 1936. Some subsequent English editions restore the notes, appendices, and bibliography omitted from the first English edition. Karl Marx: His Life and Environment is a 1939 biography of Karl Marx by Isaiah Berlin, in which Berlin argues that Marx's system of thought depends upon indefensible metaphysical presuppositions. Karl Marx: His Life and Thought is a 1973 biography of Karl Marx by political scientist David McLellan.