The material world is that which we observe physically surrounding ourselves.
While very important in terms of keeping ourselves alive through the production of food, shelter, etc., it is a diversion from the spiritual task we are concerned with as seekers and believers in a higher plane. It is true that we must meet our material needs in order to live in God, but it is more importantly true that we must shy away from material aggrandizement in order to stay pure in our pursuit of the Word.