According to critics, this also creates another problem for Marxism. If the superstructure also influences the base then there is no need for Marx's constant assertions that the history of society is one of economic class conflict. This then becomes a classic chicken or the egg argument as to whether the base or the superstructure comes first. Peter Singer proposes that the way to solve this problem is to understand that Marx saw the economic base as ultimately real. Marx believed that humanity's defining characteristic was its means of production and thus the only way for man to free himself from oppression was for him to take control of the means of production. According to Marx, this is the goal of history and the elements of the superstructure act as tools of history.