Allyn and Bacon.
Children demonstrate the ability to reason systematically in reference to tangible objects.
Classification and ordering of objects is possible. Adolescents and adults can demonstrate the ability to reason in hypothetical terms about abstract issues. Combinatorial thinking and propositional logic may be applied to solve problems presented in any format, and adolescents can generate and evaluate all possible solutions according to truth-table logic. Mechanisms of development Piaget claimed that the individual constantly strives to reach mental equilibrium , but that this mental balance or homeostasis is challenged by spontaneous interactions with the environment. New information encountered is assimilated into existing cognitive structures or schemes.