Kohlberg's stages of moral development are planes of moral adequacy conceived by Lawrence Kohlberg to explain the development of moral reasoning. Created while studying psychology at the University of Chicago, the theory was inspired by the work of Jean Piaget and a fascination with children's reactions to moral dilemmas. He wrote his doctoral dissertation at the university in 1958, outlining what are now known as his stages of moral development.
This theory holds that moral reasoning, which is the basis for ethical behavior, has six identifiable developmental constructive stages - each is more adequate at responding to moral dilemmas than the last. In studying these Kohlberg followed the development of moral judgment far beyond the ages originally studied earlier by Piaget, who also claimed that logic and morality develop through constructive stages. Expanding considerably upon this groundwork, it was determined that the process of moral development was principally concerned with justice and that its development continued throughout the lifespan, even spawning dialogue of philosophical implications of such research.
Kohlberg used stories about moral dilemmas in his studies, and was interested in how people would justify their actions if they were put in a similar moral crux. He would then categorize and classify evoked responses into one of six distinct stages. These six stages are broken into three levels: pre-conventional, conventional and post-conventional.