Michael McConnell, a Law Professor at Stanford, offers this in a First Things review of Philip Hamburger’s new book titled Law and Judicial Duty:
Hamburger traces the development of modern conceptions of the law to the realization, in Europe and especially Britain, that human reason rarely provided clear answers to moral questions and therefore that an attempt to ground law in divine will, or a search for abstract reason and justice, would inevitably lead to discord. As a result, “Europeans increasingly located the obligation of law in the authority of the lawmaker rather than the reason or justice of his laws.” The task of judges, then, was not to seek after elusive notions of justice and right reason but to enforce the law of the land. Natural law shifted in emphasis from moral content to legitimacy and authority, and increasingly to an understanding of authority based on the will of the people.
This seems to me a profound explanation of how and why we understand law today the way we do. It simultaneously shows you what is wrong with the modern conception of the law and what is right.