This text reviews theoretical bases for bioethics including definitions of morals, ethics, metaethics, bioethics and the role of health care professionals. Theory includes discussion of philosphical ethical systems, such as utilitarianism, denotology and natural law, and moral theology and religion as source and reason for ethics. The natural law theory of moral development is described in terms of Jean Piaget, Lawrence Kohlberg, James Rest, Carol Gilligan and others. One way to understand this is to see people as moral beings. This includes nurses and other health care professionals who make bioethical decisions.