Lawrence Kohlberg developed a theory of moral development that outlined six stages within three levels of moral reasoning: pre-conventional, conventional, and post-conventional. He based his theory on interviews with subjects presented with moral dilemmas like the Heinz dilemma. While influential, Kohlberg's theory has been criticized for using artificial dilemmas, a biased male sample, and not fully accounting for factors influencing moral behavior beyond reasoning. Questions also remain about whether moral judgment directly matches behavior and if justice is the sole fundamental moral principle.