The arguments of policy which, after political arguments, are the most common, are those on questions of law.  As we have seen a few pages back, such arguments are settled by the judges, while questions of fact are left to the jury.  In the White Murder Case, in which Daniel Webster made a famous argument, it was a question of fact for the jury whether the defendant Knapp was in Brown Street at the time of the murder, and whether he was there for the purpose of aiding and abetting Crowninshield, the actual murderer; the question whether his presence outside the house would make him liable as a principal in the crime was a question of law.  This distinction between questions of fact and questions of law is one of the foundation principles of the common law.  From the very beginning of the jury system, when the jury consisted of neighbors who found their verdict from their own knowledge of the case, to the present day when they are required carefully to purge their minds of any personal knowledge of the case, the common law has always held that in the long run questions of fact can best be settled by average men, drawn by lot from the community.  Questions of law, on the other hand, need learning and special training in legal reasoning, for the common law depends on continuity and consistency of decision; and a new case must be decided by the principles which have governed like cases in the past.

Nevertheless, these principles, which are now embodied in an enormous mass of decisions by courts all over the English-speaking world, are in essence a working out into minute discriminations of certain large principles, which in turn are merely the embodiment of the practical rules under which the Anglo-Saxon race has found it safest and most convenient to live together.  They settle in each case what, in view of the interests of the community as a whole and in the long run, and not merely for the parties now at issue, is the most convenient and the justest thing to do.  Mr. Justice Holmes, of the Supreme Court of the United States, wrote before his appointment to that bench: 

“In substance the growth of the law is legislative.  And this in a deeper sense than that what the courts declare to have always been the law is in fact new.  It is legislative in its grounds.  The very considerations which judges most rarely mention, and always with an apology, are the secret roots from which tine law draws all the juices of life.  I mean of course considerations of what is expedient for the community concerned.  Every important principle which is developed by litigation is in fact and at bottom the result of move or less definitely understood views of public policy; most generally, to be sure, under our practices and traditions, the unconscious result of instinctive preferences and inarticulate convictions, but none the less traceable to views of public policy in the last analysis."[2]