Orthodox Marxism
The emergence of orthodox Marxism is associated with the latter works of Friedrich Engels, such as the "Dialectics of Nature" and "", which were efforts to popularise the work of Karl Marx, render it systematic and apply it to the fundamental questions of philosophy. Daniel De Leon, an early American socialist leader, contributed much to the thought during the final years of the 19th century and the early 20th century. Orthodox Marxism was further developed during the Second International by thinkers such as Georgi Plekhanov and Karl Kautsky in Erfurt Program and The Class Struggle (Erfurt Program).