Interdependence means a dependence between autonomous elements through the formation of a combined overall organization. The essence of interdependence involves autonomy, differentiation, and emergency. Two or more autonomous elements interacting, differentiating their states with respect to each other, to create some combined organization that is greater than any of the parts, through the process of emergence. Interdependence is one of the central concepts within systems theory in that most definitions for a system involve the idea of interdependency between a set of parts. Indeed the idea of interdependency is often the central concept that is used to define a system, in that without interdependency between parts there is no system just a set of independent elements.