This document summarizes the theories of Piaget, Erikson, and Kohlberg on child development and moral reasoning. [1] Piaget identified four stages of cognitive development from infancy to adulthood. [2] Erikson described eight psychosocial stages from infancy to late adulthood defined by psychosocial crises. [3] Kohlberg identified three levels of moral reasoning - pre-conventional, conventional, and post-conventional - defined by the reasons given for moral decisions.