Kohlberg's stages of moral development were conceived by Lawrence Kohlberg to explain the development of moral reasoning. This theory holds that moral reasoning, which is the basis for ethical behavior, has six identifiable developmental stages. He followed the development of moral judgment beyond the ages originally studied by Piaget, who claimed that logic and morality develop through constructive stages. Kohlberg expanded considerably on this groundwork, determining that the process of moral development was principally concerned with justice and that its development continued throughout the lifespan, even spawning dialog of philosophical implications of his research. Kohlberg used stories about moral dilemmas in his studies, and was interested in how people would act 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 where broken into three levels: pre-conventional, conventional and post-conventional. His theory is based on constructive developmental stages; each stage and level is more adequate at responding to moral dilemmas than the last.