The original architecture for developmental stages was laid out by Jean Piaget’s studies of cognitive development over a period of forty years from the nineteen thirties to the seventies. See The Essential Piaget (NY, Basic Books) 1977. Erik Erikson added a broader psychological framework in Childhood and Society in 1950 and Identity and the Life-Cycle in 1959. Abraham Maslow described the stages of motivational development in Toward a Psychology of Being in 1968. Lawrence Kohlberg developed his theory of stages of moral development in the sixties and seventies. Carol Gilligan refined and revised Kohlberg’s stage-theory as it applies to women in A Different Voice in 1982.

In Transformations of Consciousness (Boston, Shambhala, 1986), Ken Wilber inserts earlier work into a larger framework, and includes Eastern thought. He calls this “full spectrum psychology.” He also devotes extensive discussion to various schools of psychoanalytic thought of the period from the nineteen sixties to the eighties. He includes the works of Margaret Mahler, Otto Kernberg, D. W. Winnicott, Hans Kohut and others. This work extensively revised the definition of the early stages of child development proposed by earlier research and provides a definitive foundation for thinking about stages of spiritual development. Wilber’s book provides a brief yet thorough summary of this scientific material.