This book, the last one written by Piaget, presents a new line of
empirical studies based on a revised formulation of his theory of the
development of logical reasoning. The amended theory overcomes many
problems and criticisms of his earlier formulations by providing a fresh
explanation for the origin of mental operations and mental organization
based on the concept of meaning. It also offers a more elegant vision of
the continuity in mental development from birth to adulthood. As the
final revision of Piaget's theory -- and one that opens up new areas of
inquiry -- this book calls for a reinterpretation of his earlier work --
a task which will occupy scholars for decades to come.