This article criticizes the preference for traits and abilities on the one hand, and balance and equilibrium on the other. Instead, emphasis is given to the study of the temporal order of concrete events brought about by conflicts and contradictions. In order to analyze event sequences and contradictions, the dialogue should serve as a basic topic and form of inquiry. Dialogues represent short-term changes. They need to be supplemented by studies of long-term changes during the life span of individuals and the history of society, A dialectical theory emphasizes contradictions and their synchronizations in short-and long-term development, both in the individual and in society.

In cross-sectional comparisons of their original scores, nonsurviving, older subjects and those who refused to be retested scored consistently below retestees. These results point to the heterogeneity of the aging population and to biases in the sampling process. Analysis of scores by going backward in age (negative age) starting with the time of death as the zero point suggests the occurrence of lower limits in performance (lethal limit). Decline with age is attributed to a sudden drop in performance occurring within 5 years prior to the death of subjects (terminal drop). Throughout adulthood, performances of long-term survivors are unchanged. The decline with age observed in cross-sectional studies is attributed to the increasing number of subjects exhibiting terminal drops.

Arguments for an extension of Piaget’s theory of cognitive development have been derived from philosophical and historical consideration of modern natural sciences. Implicit contradictions, which characterize these sciences as well as common thought, can be systematically apprehended only through a dialectic reinterpretation. The dialectic basis of Piaget’s theory is expressed in his assimilation-accommodation paradigm. But development is interpreted as a continuing alienation from this basis culminating in the noncontradictory thinking of formal operations. Although Piaget’s interpretations capture a rich variety of performances during childhood, they fail to represent adequately the thought and emotions of mature and creative persons. For an interpretation of adulthood and aging, a return to the dialectic basis is necessary. Such a reorganization can proceed from any of the four major levels of development. It introduces intra- and interindividual variations into Piaget’s theory. Individuals may operate simultaneously or in short succession at different cognitive levels. The ceaseless striving toward formal operations becomes inappropriate and ineffective for the level of dialectic maturity.