Friedrich Carl von Savigny was professor at Berlin, tutor to the Prussian crown prince, and eventually minister for legislative revision. His decisive intervention came in 1814, when Thibaut proposed that Germany adopt a single civil code on the French model as an instrument of national unification.
Savigny's reply, On the Vocation of Our Age for Legislation and Jurisprudence, argues that the proposal misunderstands what law is. Law is not made; it grows. It originates in the customs and beliefs of a people — the Volksgeist — in the way language does, developing organically with the nation and dying when the nation loses its individuality. Legislation can register and refine what has developed, but a code drafted from principle imposes on a living body a form taken from somewhere else, and freezes at one moment what ought to keep moving. Germany, he concluded, was not yet ripe for codification, and what was needed first was historical scholarship: a proper understanding of Roman law as it had actually been received and modified in German practice.
He won. Codification was deferred for the better part of a century, and the Civil Code of 1900 was drafted by scholars formed in his school, using the conceptual apparatus his research had built. His own System of Modern Roman Law reconstructed the sources with an exactness that founded modern legal scholarship, and his account of the legal transaction, of declarations of will and of possession shaped continental private law permanently.
The argument's reach extends well past law. It is the same move Herder made about language and Burke about constitutions, applied to the one domain where legislators most confidently believe they are simply choosing, and it made the historical school the dominant force in nineteenth-century German jurisprudence. Marx, who attended his lectures and detested them, wrote an early polemic against the school for making whatever exists appear legitimate by tracing its pedigree. Maine's comparative jurisprudence in England and the sociological approaches to law that followed both stand in its debt, and every subsequent argument that transplanted law fails without the culture it came from is Savigny's.