Final answer:
According to Kohlberg's theory of moral development, people must consider universal ethical principles to reason at the post-conventional level.
Step-by-step explanation:
According to Kohlberg's theory of moral development, in order to reason at the post-conventional level, people must consider universal ethical principles. This means that individuals at this level of moral reasoning focus on abstract and universal principles, such as justice and human rights, rather than just following societal norms or conforming to authority figures. For example, someone at the post-conventional level might believe that it is morally right to steal a life-saving drug for a loved one, even if it goes against the laws or social norms.