Maslow defines the personality structure in terms of being able to progress up the pyramid of self- actualization. For Maslow, the hierarchy establishes some of the basic needs like shelter and food. Maslow argues that the structure of the personality is reflective of progression of self- actualization. The personality cannot effectively advance to more thought provoking and complex elements if the basic elements are not met. Struggling for shelter or basic elements such as food and water help to preclude a full development of the personality. Its structure and the arc of its development are dependent on the ability to have these basic elements met and then progression happens from here. A collision between both "higher" and "lower" needs could reveal much about the nature of the personality and how its development has transpired. In the end, the structure of the personality is seen in Maslow's theory as one that progresses from the achievement of those needs seen as "basic" and along the more complex and emotional nuanced needs that help to define being. In this, Maslow makes it clear that the structure of the personality is defined by a classification of particular needs in the lives of the individuals.