state intervention ceased, these types of incomes would disappear due to increased competition in capital. Although Proudhon opposed this type of income, he expressed that he "never meant to [...] forbid or suppress, by sovereign decree, ground rent and interest on capital. I believe that all these forms of human activity should remain free and optional for all". Mutualists argue for conditional titles to land, whose private ownership is legitimate only so long as it remains in use or occupation (which Proudhon called "possession"). Proudhon's mutualism supports labor-owned cooperative firms and associations for "we need not hesitate, for we have no choice [...] it is necessary to form an ASSOCIATION among workers [...] because without that, they would remain related as subordinates and superiors, and there would ensue two [...] castes of masters and wage-workers, which is repugnant to a free and democratic society" and so "it becomes necessary for the workers to form themselves into democratic societies, with equal conditions for all members, on pain of a relapse into feudalism". As for capital goods (man-made and non-land, means of production), mutualist opinion differs on whether these should be common property and commonly managed public assets or private property in the form of worker cooperatives, for as long as they ensure the worker's right to the full product of their labor, mutualists support markets and property in the product of labor, differentiating between capitalist private property (productive property) and personal property (private property). Following Proudhon, mutualists are libertarian socialists who consider themselves to part of the market socialist tradition and the socialist movement. However, some contemporary mutualists outside the classical anarchist tradition abandoned the labor theory of value and prefer to avoid the term socialist due to its association with state socialism throughout the 20th century. Nonetheless, those contemporary mutualists "still retain some cultural attitudes, for the most part, that set them off from the libertarian right. Most of them view mutualism as an alternative to capitalism, and believe that capitalism as it exists is a statist system with exploitative features". Mutualists have distinguished themselves from state socialism and do not advocate state ownership over the means of production. Benjamin Tucker said of Proudhon that "though opposed to socializing the ownership of capital, Proudhon aimed nevertheless to socialize its effects by making its use beneficial to all instead of a means of impoverishing the many to enrich the few [...]