In this way things, external objects, are assimilated to more or less ordered motor schemas, and in this continuous assimilation of objects the child… - Jean Piaget

Between the various types of rules which we shall give there will therefore be at once continuity of function and difference of structure. This renders arbitrary any attempt to cut mental reality up into stages. The matter is further complicated by the "Law of conscious realization" and the resulting time-lag. The appearance of a new type of rule on the practical plane does not necessarily mean that this rule will come into the subject's consciousness, for each mental operation has to be relearned on the different planes of action and of thought.

For someone who constantly comes across this problem in the course of his professional activities, the question whether philosophy has the status of a “wisdom” or of a form of “knowledge” peculiar to itself is no longer an unnecessary or simply a theoretical problem; it is a vital question, since it affects the success or failure of thousands of scholars.

The child who defines a lie as being a "naughty word" knows perfectly well that lying consists in not speaking the truth. He is not, therefore, mistaking one thing for another, he is simply identifying them one with another by what seems to us a quaint extension of the word "lie".