economies and the establishment of prostitution as a "fundamental feature of human civilization". Similarities between wage labor and slavery were noted in ancient Rome by Cicero while the pervasive practice of voluntary slavery in Medieval Russia indicates the previous historical coexistence of slavery and voluntary choice. Before the American Civil War, Southern defenders of African American slavery invoked the concept of wage slavery to favorably compare the condition of their slaves to workers in the North. With the advent of the Industrial Revolution, thinkers such as Proudhon and Marx elaborated the comparison between wage labor and slavery in the context of a critique of societal property not intended for active personal use while Luddites emphasized the dehumanization brought about by machines. Emma Goldman famously denounced wage slavery by saying: "The only difference is that you are hired slaves instead of block slaves". The introduction of wage labor in 18th-century Britain was met with resistance—giving rise to the principles of syndicalism. Historically, some labor organizations and individual social activists have espoused workers' self-management or worker cooperatives as possible alternatives to wage labor. Collectivizations and workers control Workers' control is a term meaning participation in the management of factories and other commercial enterprises by the people who work there. It has been variously advocated by anarchists, socialists, communists, social democrats and Christian democrats and has been combined with various socialist and mixed economy systems. Workers' councils are a form of workers' control. For Proudhon, mutualism involved creating "industrial democracy", a system where workplaces would be "handed over to democratically organised workers' associations [...] We want these associations to be models for agriculture, industry and trade, the pioneering core of that vast federation of companies and societies woven into the common cloth of the democratic social Republic". He urged "workers to form themselves into democratic societies, with equal conditions for all members, on pain of a relapse into feudalism". This would result in "[c]apitalistic and proprietary exploitation, stopped everywhere, the wage system abolished, equal and just exchange guaranteed". Workers would no longer sell their labour to a capitalist but rather work for themselves in co-operatives.Council communism, such as in the early Soviet Union advocated workers' control through workers councils and factory committees. Syndicalism advocates workers' control through trade unions. Guild socialism advocates workers' control through a revival of the guild system. Participatory economics represents a recent variation on the idea of workers' control.