"Jean Piaget was preoccupied, late in life, with the developing child's understanding of possibility--how the child becomes aware of the potentially unlimited scope of possible actions and learns to choose among them. Piaget's approach to this question took on a new openness to real-life situations, less deterministic than his earlier, ground-breaking work in cognitive development. The resulting two-volume work in cognitive development. The resulting two-volume work--his last--was published in France in 1981 and 1983 and is now available for the first time in English translation. Possibility and Necessity combines theoretical interpretation with detailed summaries of the experiments that Piaget and his colleagues used to test their hypotheses. "Piaget's intent, in Volume 1, is to explore the process whereby possibilities are formed. He chooses to understand the possible not as something predetermined by initial conditions; rather, in his use of the term, possibilities are constantly coming into being, and have no static characteristics--each arises from an event which has produced an opening onto it, and its actualization will in turn give rise to other openings. In perceiving that a possibility can be realized, and in acting upon it, the child creates something that did not exist before. "Volume 2 presents a series of experiments documenting the way children between the ages of four or five and eleven to thirteen come to develop a grasp of necessity and its role in understanding the world about them. The experiments show how children proceed from an initial level (at four or five years) of pseudo-necessities, where they see the world as necessarily what it appears to be without the existence of possibilities, to an intermediate level (at six to ten years), where pseudo-necessities give way to increasingly rich arrays of possibilities and a final stage (at eleven to thirteen years), where children are able to select among these multiple possibilities the one that fits all the data. This stage represents the optimal level of understanding reality, which is now seen by the child as infinitely variable, yet coherent and lawful. Psychologically, this lawfulness corresponds to a sense of necessity, or certainty."