Marx and Engels’ works contain highly rich descriptions about the unstable, fragmented and heterogeneous character of the proletariat’s relationship both with cultural dynamics of industrial cities and political practices of the time. One of the most controversial concepts in this particular context is lumpenism. The literature regarding the use of the term lumpen (proletariat) in Marxist classics usually and mainly focuses on Marx’s writings on 1848 French revolutions and the role attributed to the declassed poor in the defeat of revolutions. However, Engels’s vivid portrayal of working-class culture and identity, especially in The Condition of English Working Class, suggests a much further and larger scope as far as lumpenism is concerned –i.e. ethico-political formation of the proletariat as the agency of a social and political revolution. By scanning mainly Engels’ work, this article focuses on the following questions: Does the category of lumpen offer any analytical function in terms of structural class analysis based on production relations? How is the concept lumpen relevant to the debate on the political agency and potency of the working class, especially in terms of divergence between Marxism and other (early) socialist doctrines? How can we assess the moralist implications of degeneration inherent in the concept of “lumpen”, especially considering the relationship between bourgeois moralism of the 19th century and Marxism?