According to Marx, the conflict created by the contradictory positions of two groups, the proletariat and the capitalists, is at the heart of capitalism. Because these represent groups in conflict, Marx called them classes. For Marx, every period of history contained fault lines upon which potential conflict could result, and, thus, every historical period had its own class formations. Because capitalists are continually accumulating capital while also competing with other capitalists, Marx believed that more and more members of society would eventually become proletarians in a process he called proletarianization. Society would then be characterized by a very small number of capitalists exploiting a large number of poor proletarians subsisting on low wages. Marx called this group of proletarians the industrial reserve army. Thus, the normal operation of the capitalist system, through competition and exploitation, produces an ever greater number of workers who will eventually rise up to overthrow the system.