Radical party that affirms "the maintenance of private property"? Used in this general and abstract fashion the phrase "private property" has no meaning whatever.
In the course of human evolution private property has many times changed its form and its substance, its meaning and its scope.
In the societies that preceded ours private property embodied itself in forms of oppression which have been definitely abolished once for all. Slavery was one of the forms of private property. In Athens and Rome there were public slaves, slaves of the city or the state; but most of the slaves were simply a part of the patrimony of the citizens. The property in slaves was part of private property. The slaves either cultivated the lands of their Greek or Roman master or they laboured for his profit in the city workshops. Individuals owned them, disposed of them, forced them to labour, gave them away as presents, sold them, or left them to their heirs. And in the same way, when, after the collapse of the ancient society and the Roman régime founded on conquest, slavery was ameliorated and became serfdom, the serfs, too, bound to the land, were objects of certain private property rights. Under the Merovingian and Carlovingian kings there were royal slaves attached to the royal lands, and Church slaves attached to the Church lands, but the immense majority of the serfs belonged to lords who were in the end practically great landed