system. This movement can be intragenerational or intergenerational. Such mobility is sometimes used to classify different systems of social stratification. Open stratification systems are those that allow for mobility between, typically by placing value on the achieved status characteristics of individuals. Those societies having the highest levels of intragenerational mobility are considered to be the most open and malleable systems of stratification. Those systems in which there is little to no mobility, even on an intergenerational basis, are considered closed stratification systems. For example, in caste systems, all aspects of social status are ascribed, such that one's social position at birth persists throughout one's lifetime. Karl Marx In Marxist theory, the modern mode of production consists of two main economic parts: the base and the superstructure. The base encompasses the relations of production: employer–employee work conditions, the technical division of labour, and property relations. Social class, according to Marx, is determined by one's relationship to the means of production. There exist at least two classes in any class-based society: the owners of the means of production and those who sell their labor to the owners of the means of production. At times, Marx almost hints that the ruling classes seem to own the working class itself as they only have their own labor power ('wage labor') to offer the more powerful in order to survive. These relations fundamentally determine the ideas and philosophies of a society and additional classes may form as part of the superstructure. Through the ideology of the ruling class—throughout much of history, the land-owning aristocracy—false consciousness is promoted both through political and non-political institutions but also through the arts and other elements of culture. When the aristocracy falls, the bourgeoisie become the owners of the means of production in the capitalist system. Marx predicted the capitalist mode would eventually give way, through its own internal conflict, to revolutionary consciousness and the development of more egalitarian, more communist societies. Marx also described two other classes, the petite bourgeoisie and the lumpenproletariat. The petite bourgeoisie is like a small business class that never really accumulates enough profit to become part of the bourgeoisie, or even challenge their status. The lumpenproletariat is the underclass, those with little to no social status. This includes prostitutes, beggars, the homeless or other untouchables in a given society. Neither of these subclasses has much influence in Marx's two major classes, but it is