directed at Piaget. We do not have room, in this book, to discuss this criticism
of his work. We would merely like to say that much of it arises either from
insufficient knowledge of Piaget's ideas, or from conflicting ideology. An
author who is convinced that knowledge is basically social in nature, or who
believes that knowledge structures are innate, naturally cannot accept a theory
that tends to validate the point of view that neither social factors nor innate
abilities play a major role.

We do not wish to imply that Piaget's work is above criticism. The fact that
he constantly preferred to add ideas, new formulations, or facts to his previous
work rather than clarify or carry out a synthesis of the contents raises a number
of questions. When all is said and done, however, knowledge of Jean Piaget's
theory and of his experimental contributions is a kind of intellectual compe-
tence desirable in facing new challenges in psychological science. Scientific
work falls, in fact, into two categories: There are, on one hand, models with a
great many applications and, on the other hand, heuristic theories. The former
have broad explanatory power and are easily generalized to new prob-
lems--until the day comes when they are replaced by others. Heuristic
theories are more difficult to apply to facts, but they stimulate reflection and
research. Piaget's work belongs to this second category of fertile, productive
theories.

There are four main reasons why knowledge of Piaget's theory is so
important. The first is the stimulating aspect mentioned earlier: Most
readers of Piaget's work or of extracts from it do not remain indifferent,
but reflect on what he says--even if this reaction is critical--and often
come up with ideas for research. The second reason is that Piaget was a
precursor; some of the broad perspectives he adopted and most of his
explanatory concepts, even though many of them were conceived in the
first half of the 20th century, prefigure perspectives and concepts of
contemporary psychology. Piagetian psychology was, for example, mental-
istic, refusing to stop at the observation of behavior, long before the
American cognitivist revolution of the late 1960s. It defined functional
units 30 to 40 years before the concepts of frame and schema were
conceived. In the 1940s, Piaget used the concept of regulation, which is of
capital importance in present-day perspectives of cybernetics and in the
study of self-organizing systems. His work has therefore been justly classi-
fied as belonging to "cognitive science," on which the study of knowledge
depends today. A third reason for interest in Piaget's work is that he has
produced the most complete theory of intellectual development: It covers
the period from the cradle to adulthood and strives to define the links of
intelligence and logic with other cognitive functions such as memory,
language, and perception. Finally, the enormous quantity of experimental
facts concerning the development of children's knowledge justifies in itself
an acquaintance with Piaget's works. These data result from an indefatiga-
ble research activity conducted by talented collaborators over more than
half a century.

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