In all of his published work, Jean Piaget never abandoned his original theoretical framework for the understanding of human development. This framework insists that intelligence is essentially a biological phenomenon; its development is best understood as the development of a sophisticated and highly successful adaptation device. This device enables human beings to organize and structure their experience according to concepts and ideas which eventually form the complex system of objective human knowledge. This book argues that the philosophical framework of Piaget's theory of intellectual development is not empirically testable, but rests on dubious metaphysical assumptions about the nature of the human mind and about the nature of knowledge and reality. It discusses the central features of Piaget's theory and relates them to central arguments from other thinkers, ranging from Kant and Wittgenstein, through Vygotsky, to Bruner and Gibson. These arguments concern the nature of knowledge, the relation between knowledge and reality, and alternative views on the nature and direction of human development. (JMK)