If children fail to understand one another, it is because they think they understand one another. The explainer believes from the start that the repr… - Jean Piaget

intelligence, the most plastic and at the same time the most durable structural equilibrium of behaviour, is essentially a system of living and acting operations.

A second prefatory question faces us: that of society and the individual. We have sought to contrast the child and the civilized adult on the ground of their respective social attitudes. The baby (at the stage of motor intelligence) is asocial, the egocentric child is subject to external constraint but has little capacity for cooperation, the civilized adult of to-day presents the essential character of cooperation between differentiated personalities who regard each other as equals. There are therefore three types of behavior: motor behavior, egocentric behavior (with external constraint), and cooperation. And to these three types of social behavior there correspond three types of rules: motor rules, rules due to unilateral respect, and rules due to mutual respect. But here again, one must beware of laying down the law: for things are motor, individual and social all at once. As we shall have occasion to show, rules of cooperation are in some respects the outcome of the rules of coercion and of the motor rules. On the other hand, coercion is applied during the first days of an infant's life, and the earliest social relations contain the germs of cooperation. Here again, it is not so much a question of these successive features themselves as of the proportions in which they are present. Moreover, the way in which conscious realization and the time-lag from one level to another come into play is a further bar to our arranging these phenomena in a strict sequence, as though they made a single appearance and then disappeared from the scene once and for all.

Thus, even in those fields in which logic does not normally play a part, there exist outline structures which are the precursors of logical structures, and which can be formulated in terms of the algebra of logic. From a comparative point of view, these outline structures are of great interest. It is not inconceivable that a general theory of structures will at some future date be worked out, which will permit the comparative analysis of structures characterizing the different levels of development. This will relate the lower level outline structures to the logical structures characteristic of the higher stages of development. The use of the logical calculus in the description of neural networks on the one hand, and in cybernetic models on the other, shows that such a programme is not out of the question.