Children should be able to do their own experimenting and their own research. Teachers, of course, can guide them by providing appropriate materials,… - Jean Piaget

Every structure is to be thought of as a particular form of equilibrium, more or less stable within its restricted field and losing its stability on reaching the limits of the field.

Before games are played in common, no rules in the proper sense can come into existence. Regularities and ritualized schemas are already there, but these rites, being the work of the individual, cannot call forth that submission to something superior to the self which characterizes the appearance of any rule.

Egocentrism in so far as it means confusion of the ego and the external world, and egocentrism in so far as it means lack of cooperation, constitute one and the same phenomenon. So long as the child does not dissociate his ego from the suggestions coming from the physical and from the social world, he cannot cooperate, for in order to cooperate one must be conscious of one's ego and situate it in relation to thought in general. And in order to become conscious of one's ego, it is necessary to liberate oneself from the thought and will of others. The coercion exercised by the adult or the older child is therefore inseparable from the unconscious egocentrism of the very young child.