Thus finally we must abandon even the title. It is not the proletariat that is being formed into a class: it is a variety of persons some of whom are separated from the system of production. Processes of forming workers into a class do not take place in a vacuum; rather, they are inextricably tied to the totality of processes through which collectivities appear in struggle at particular moments of history. And the outcomes of these processes, while not arbitrary, are not determined uniquely by the structure of social relations. More than one outcome lies within the limits set by those relations.

"Proletariat into a Class: The Process of Class Formation from Karl Kautsky's The Class Struggle to Recent Controversies", Politics & Society (1977)