ABSTRACT
Proponents of natural law believe there is a fundamental and unchanging law common to all human beings and accessible through reason. Natural-law theory is usually contrasted to positive-law theory, which maintains that law is based upon the will of the sovereign and is manifested in human laws or constitutions. For most natural-law theorists, natural law is founded in the eternal law of God. In Treatise on Law, written in the thirteenth century, Catholic theologian Saint Thomas Aquinas divided laws into four types: eternal, natural, human, and divine. He defined natural law as the rational creature's participation in the eternal law. In the nineteenth century, natural-law theory was attacked by the emerging legal-positivist school, whose advocates contended that law is simply what the sovereign says it is. Federal judges in ascertaining the appropriate common law, guided by their reason, would in essence be applying "natural law." .
