Again, tenth, men have thought of law as a system of principles, discovered philosophically and developed in detail by juristic writing and judicial decision, whereby the external life of man is measured by reason, or in another phase, whereby the will of the individual in action is harmonized with those of his fellow men. This mode of thought appeared in the nineteenth century after the natural-law theory in the form in which it had prevailed for two centuries had been abandoned and philosophy was called upon to provide a critique for systematic arrangement and development of details. Eleventh, law has been thought of as a body or system of rules imposed on men in society by the dominant class for the time being in furtherance, conscious or unconscious, of its own interest. This economic interpretation of law takes many forms. In an idealistic form it thinks of the inevitable unfolding of an economic idea. In a mechanical sociological form it thinks of class struggle or a struggle for existence in terms of economics, and of law as the result of the operation of forces or laws involved in or determining such struggles. In a positivist-analytical form it thinks of law as the command of the sovereign, but of that command as determined in its economic content by the will of the dominant social class, determined in turn by its own interest. All of these forms belong to transition from the stability of the maturity of law to a new period of growth. When the idea of the self-sufficiency of law gives way and men seek to relate jurisprudence to the other social sciences, the relation to economics challenges attention at once. Moreover in a time of copious legislation the enacted rule is easily taken as the type of legal precept and an attempt to frame a theory of legislative lawmaking is taken to give an account of all law. Finally, twelfth, there is an idea of law as made up of the dictates of economic or social laws with respect to the conduct of men in society, discovered by observation, expressed in precepts worked out through human experience of what would work and what not in the administration of justice. This type of theory likewise belongs to the end of the nineteenth century, when men had begun to look for physical or biological bases, discoverable by observation, in place of metaphysical bases, discoverable by philosophical reflection. Another form finds some ultimate social fact by observation and develops the logical implications of that fact much after the manner of the metaphysical jurist. This again results from the tendency in recent years to unify the social sciences and consequent attention to sociological theories.