Possibility and Necessity was first published in 1987. Minnesota Archive Editions uses digital technology to make long-unavailable books once again accessible, and are published unaltered from the original University of Minnesota Press editions.

Jean Piaget was preoccupied, later 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—his last—was published in France in 1981 and 1983 and is not 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.

To observe this process, Piaget and his associates devised a series of thirteen problems appropriate for children ranging in age from four or five to eleven or twelve; they were asked to name all possible ways three dice might be arranged, for example, or a square of paper sectioned. The experimenters had two primary aims—to discover to what extent the child's capacity to see possibilities develops with age, and to determine the place in cognitive development of this capacity—does it precede or follow the advent of operational thought structures? In charting this process, Piaget discerns a growing interaction between possibility and necessity. How the child comes to understand necessity and achieves a dynamic synthesis—or equilibrium — between the possible and the necessary is discussed by Piaget and his colleagues in Volume 2, The Role of Necessity in Cognitive Development, also published by Minnesota.

Possibility and Necessity was first published in 1987. Minnesota Archive Editions uses digital technology to make long-unavailable books once again accessible, and are published unaltered from the original University of Minnesota Press editions.

This two-volume work—Jean Piaget's last—was published in France in 1981 and 1983 and is available now for the first time in English translation. Reflecting the preoccupations and methodologies of his later years, Possibility and Necessity combines theoretical interpretation with detailed summaries of the experiments Piaget and his colleagues used to test their hypotheses.

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 other 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.

Volume 2 thus completes the theory presented in Volume 1 (The Role of Possibility in Cognitive Development) by showing how cognitive development is mediated on the one hand by a dialectical process of ever-expanding possibilities and, on the other, by increasingly delimiting necessities. In demonstrating how this process operates in psychological development—and in pointing out analogies in the history of science — Piaget gave his genetic epistemology its final and most accomplished form. The acquisition of knowledge is thus shown to be the result of two complementary processes: the formation of possibilities and the grasping of necessary laws and constraints in the construction of a reasoned representation of the external world.