Nor could the eighteenth century codes achieve the completeness of statement or permanence of content expected of them. They were chiefly successful in unifying the law where there had been an inconvenient diversity of local law. They have had to be amended and supplemented and a mass of doctrinal and judicial interpretation and application has had to grow up around them and new codes have had to be drawn up and more are urged upon wholly new lines and theories.
Lord Mansfield’s attempt to settle all parts of English common law on rational principles, although it achieved much, especially in commercial law, on the whole failed.78 Pure reason and the example of the modernized Roman law of the Continent did not suffice to enable him to make the common-law courts into courts of equity, to do away with the technical medieval rules of the law of real property, nor to put the common law as to simple contracts on a rational and moral basis. He was more than a century ahead of his time. What he sought to do and much more has been done since under the auspices of a different philosophy.
Likewise the natural-law theory of American constitutional law had ill results from which administration of justice in America has been suffering for two generations. It led to a doctrine of constitutional provisions as declaratory of natural law and so to an ideal of the common law as in its main lines and characteristic doctrines an embodiment of universal precepts running back of all constitutions. Thus certain common-law doctrines and traditionally received ideals of the profession were made into a superconstitution by which the social legislation of the last decade of the nineteenth century and of the first third of the present century was to be judged.79
At the end of the eighteenth century Kant undermined the method of the law-of-nature school of the two preceding centuries.80 For a time the place held by theology in the Middle Ages and by reason in the seventeenth and eighteenth centuries was taken by history and philosophical jurisprudence was carried on by a metaphysical school which sought to work out an ideal critique of legal institutions, legal doctrines and legal precepts deduced from a metaphysically given fundamental idea of right or some simple fundamental formula of justice.81 Where the law-of-nature school thought of an ideal body of detailed legal precepts, the metaphysical jurists thought rather of an ideal element in the law and a critique of legal precepts on the basis of that element. Conceiving of the ideal element as the significant part of the law they rejected the law-of-nature theory of law made consciously to the pattern of rationally discovered universally valid precepts and held with the historical jurists that law was found not made. It was found by experience, said the historical jurists,82 and in that experience, said the Hegelian later metaphysical jurists, an ideal of right or an idea of freedom was realizing itself.83 In England and the United States it has been customary to speak lightly of this school and to assume that their speculations were wholly in the air.84 It is true they did not directly and immediately affect the actual course of judicial decision and juristic writing. But Kant formulated the idea of justice which was universally accepted in the nineteenth century and obstinately held on in American constitutional law in the first third of the present century. Through their influence upon the historical school of jurists, which was dominant in the latter part of the nineteenth century, they fixed the lines of the ethical interpretation of legal history and gave content to the idea of freedom which historical jurists postulated as unfolding in legal development. Maine’s famous generalization that the history of law is the record of a progress from status to contract85 simply puts in concrete form the cardinal idea of the metaphysical school.
At the end of the nineteenth century the then dominant historical school of jurists all but displaced philosophical jurisprudence. In the present century a revived philosophy of law took form in a social-philosophical school, social utilitarians, Neo-Kantians, and Neo-Hegelians,86 more or less merging later in a neo-idealist type.87 In the fore part of the nineteenth century lines of cleavage involved in divergent aspects of eighteenth-century philosophical jurisprudence and different phases of reaction from the law-of-nature school, brought about a separation of jurists into three well-defined schools: historical, metaphysical, and analytical.88 The nineteenth century was the century of history as the thirteenth was the century of theology, at any rate in jurisprudence, and the seventeenth and eighteenth centuries were the centuries of reason. The historical jurists carried forward the doctrine of those eighteenth-century jurists who held that legislation and precepts of positive law were merely declaratory. The law-of-nature jurists said they were declaratory of reason. The historical jurists said they were declaratory of social experience in the administration of justice in which an idea of right or an idea of freedom was unfolding. The metaphysical school sought to demonstrate an unchallengeable basis to replace pure reason and thus provide an assured critique of law from the outside. The analytical school carried forward another trend in eighteenth-century theory which had conceived of an authoritative declaration of natural law by the sovereign. Thus all three of the nineteenth-century schools have the doctrine of the law-of-nature school in their pedigree. Bentham taught something very like a natural law derived from his theory of utility. Austin89 and Holland90 gave us what was very like a ius gentium, a system of law reached by reason applied to comparative law. The metaphysical school, the philosophical school of the last century, definitely disappeared by the beginning of the twentieth century. The historical school and the analytical school still have adherents, but both have been largely superseded by new types of juristic thought.
In social philosophical jurisprudence the most influential group has been the Neo-Kantians. Their founder and leader, Rudolf Stammler (1856–1938) sought to work out a universally valid method of judging as to the justice obtained by application of legal precepts in the time and place. He spoke of a natural law with a changing content. As contrasted with the eighteenth-century conception of universally valid ideal precepts, and Kant’s essay at a universal critique, Stammler sought a universally valid method of developing a relative critique whereby justice might be achieved in the time and place. His enduring work has been in formulation of the social ideal of the time and place, and his theory of the application of legal precepts where the last century thought simply of their nature. Nineteenth-century philosophical jurisprudence asked whether a particular legal precept was just. Stammler asked whether and how far justice may be attained by means of the precept. Where nineteenth-century jurists thought that if rules were abstractly just the results of the application of the rules in particular cases need not be looked into, he taught the present century to seek just results by means of legal precepts conforming to and administered in the light of social ideals.91
Josef Kohler (1849–1919) was the leader of the Neo-Hegelians. He recognized that law, while it must be stable, must nevertheless constantly change. He thought of law as a product of the civilization of a people in the past and of attempts to adjust the results of that past civilization to the civilization of the present. The adjustment must be made with reference to recognition of a continually changing civilization. The traditional legal materials must be shaped so as to further rather than retard developing culture. His most important contribution to jurisprudence is his theory of the jural postulates of the civilization of the time and place. He considers it a task of the jurist to find and formulate the principles of right assumed in or expressed by a given civilization. These postulates may serve as a critique of legal precepts. But even more received ideals may be tried with reference to them and thus clear outline may be given to the ideal of the legal order which is so large an element in the development and application of legal precepts.92
More recently there has been a tendency to merge the formerly distinct types of social-philosophical jurisprudence in what may be called a neo-idealism, which seeks to understand, organize, and criticize the ideal element in law and, in particular, to transcend nineteenth-century individualism and nineteenth-century