" Piaget-....A stage then, we may say, is an integrated set of operational structures that constitute the thought processes of a person at a given time. Development involves the transformation of such " structures of the whole" in the direction of greater internal differentiation, complexity, flexibility and stability. A stage represents a kind of balanced relationship between a knowing subject and his or her environment. In this balanced or equilibrated position the person assimilates what is to be " known" in the environment into her or his existing structures of thought. When a novelty or challenge emerges that cannot be assimilated into the present structures of knowing then, if possible, the person accommmodates, that is , generates new structures of knowing. A stage transition has occured when enough accommodation has been undertaken to require ( and make possible) a transformation in the operational pattern of the structural whole of intellectual operations. "