The concept of materialism is important to the definition of Marx's vision of history because it helps to provide the basic elements of who has wealth and who lacks it. For Marx, history has been defined by the basic premise of the "haves" vs. the "have nots." Material wealth or possession of capital is the basic element that defines how history has progressed. Marx believes that the entire narrative of human history has been rooted in the idea of who holds wealth and the ownership of the means of production as opposed to who lacks it. In this, I think that materialism,the desire to gain and proliferate personal wealth, is a reflection of how Marx has seen history progressed. The desire and need to keep and grow wealth has defined power and the relationship between control and government. Materialism for Marx is essential in this process for as more people desire and wish for wealth, this helps to tighten their control over the means of production. It also defines history because the story of how those in the position of power have kept it from those who lack this control, but wish to have power is the story for Marx's vision of human history.