For the same reason, the rules of decision already in existence are necessarily in a continuous state of change, simply on account of social evolution. This can be observed most clearly in the case of the adopted Roman law. For what was adopted was not, of course, the legal relations existing among the Romans, but merely the Roman rules of decisions, and, among these (as already stated), almost exclusively those belonging to the body of lawyers' law. Now we find ourselves confronted by this remarkable situation, that the Roman rules of decision are filled with an entirely new content by the modern, native legal relations to which they are applied.
Looking at it superficially, one might think that the Roman law of debtor and creditor was adopted almost completely. Yet, in the case of a Roman "obligatio," creditor and debtor were not individuals but groups of individuals, legally represented by the "paterfamilias," who alone could do a legal act.4 Obviously, the fact that to-day this relation is not one between groups of people but between individuals is a difference so fundamental that as against this all similarities in detail must disappear. Again, almost before our eyes, the matrimonial relation is turning from a relation of dominion of a man over a woman into an association of two individuals of equal importance and equal rights; the paternal authority and the authority of a guardian are becoming a public office instead of a private, profitable right.
Transformations of this sort, pregnant with immeasurable consequences, are likely to be at work every moment in affecting legal and social judgments concerning legal relations; yet it might not be necessary on that account to change a single line of the written law. Many a thing is to-day considered a bitter wrong done to a matrimonial partner, or a breach of faith toward a ward, which perhaps as late as the first half of the 18th or the first third of the 19th century nobody would have considered wrong. The most tremendous and irresistible legal revolutions are going on in the social institutions themselves and transform radically the rules of decision of the lawyers' law, sometimes without so much as entering into the consciousness of the parties or even of the lawyers themselves.