American jurisprudence currently applies two incompatible validity standards to determine which laws are enforceable. The natural law tradition evaluates validity by an uncertain standard of divine law, and its methodology relies on contradictory views of human reason. Legal positivism, on the other hand, relies on a methodology that commits the analytic fallacy, separates law from its application, and produces an incomplete model of law. These incompatible standards have created a schism in American jurisprudence that impairs the delivery of justice. This dissertation therefore formulates a new standard for legal validity. This new standard rejects the uncertainties and inconsistencies inherent in natural law theory. It also rejects the narrow linguistic methodology of legal positivism. In their stead, this dissertation adopts a pragmatic methodology that develops a standard for legal validity based on actual legal experience. This approach focuses on the operations of law and its effects upon ongoing human activities, and it evaluates legal principles by applying the experimental method to the social consequences they produce. Because legal history provides a long record of past experimentation with legal principles, legal history is an essential feature of this method. This new validity standard contains three principles. The principle of reason requires legal systems to respect every subject as a rational creature with a free will. The principle of reason also requires procedural due process to protect against the punishment of the innocent and the tyranny of the majority. Legal systems that respect their subjects' status as rational creatures with free wills permit their subjects to orient their own behavior. The principle of reason therefore requires substantive due process to ensure that laws provide dependable guideposts to individuals in orienting their behavior. The principle of consent recognizes that the legitimacy of law derives from the consent of those subject to its power. Common law custom, the doctrine of stare decisis, and legislation sanctioned by the subjects' legitimate representatives all evidence consent. The principle of autonomy establishes the authority of law. Laws must wield supremacy over political rulers, and political rulers must be subject to the same laws as other citizens. Political rulers may not arbitrarily alter the law to accord to their will. Legal history demonstrates that, in the absence of a validity standard based on these principles, legal systems will not treat their subjects as ends in themselves. They will inevitably treat their subjects as mere means to other ends. Once laws do this, men have no rest from evil. Advisors/Committee Members: McDermott, John J. (advisor), Pappas, Gregory (committee member), Austin, Scott W. (committee member), Welch, Ben D. (committee member).