The American Socialist theoretician and political leader Daniel De Leon (1852-1914) was, according to Lenin, "the greatest of modern Socialists--the only one who has added anything to Socialist thought since Marx." However, De Leon's Socialist Labor party remained a tiny sect.

According to his own testimony, Daniel De Leon was born into a wealthy family on the island of Curaçao near Venezuela, but it is possible that he was American-born. He was also said to have studied languages, history, philosophy, and mathematics at Dutch and German universities between 1865 and 1871. In 1872 he came to New York City and briefly assisted Cuban revolutionaries editing a Spanish-language newspaper. De Leon taught at a preparatory school and in 1876 entered Columbia University Law School. He graduated in a year and in 1883 was appointed to an international law lectureship at Columbia. He left Columbia in 1889, when he was denied a promised promotion...