Relationships, especially close relationships, are among the most important aspects of life for most of us. Close relationships reach to the very heart of our happiness --but exactly what processes or skills, over the course of a lifetime, help us learn to relate to one another more and more deeply, and to grow past the differences and problems that might divide us? Adult Development applies the concept of complex postformal thought in order to explore how certain cognitive processes support individuals close relationships such that those relationships grow stronger and richer over time. Complex postformal thought allows a person to deal with everyday logical contradictions by letting that person understand that reality and meaning are co-created. In this way, postformal thought enables adults to bridge two contradictory but logical positions and reach an adaptive synthesis of them through a higher-order logic. Taking this inquiry a step further, Sinnott examines the role played by postformal thought in intimate relationships -- those between spouses, partners, parents and children, siblings, and close friends. Sinnott argues that postformal thought seems to develop later in life and is somewhat akin to the concept of wisdom. Based on 30 years of research, this book diverges from typical contributions to this field by discussing positive adult development in the context of close relationships. Rather than focusing on the emergence of deficits of adulthood and particularly aging, Sinnott instead explores the cognitive processes that are important in creating and sustaining close ongoing relationships.