Alike in the Middle Ages, and since their close, it has been the subject of speculation and an influence guiding the legislator, the thinker, and the administrator of law.  There is a whole literature upon it on the Continent.  It bulks pretty largely in Blackstone:  you can see its influence on the judges of the eighteenth century in this country; the founders of the American Republic put a good deal of it into their constitution, and American judges will still refer to it without shame.  What it really means is a standard by which the law here and now may be judged, a standard founded on the needs of human nature.  That the standard becomes a different one, as the needs and possibilities of humanity develop, has not prevented the seeking after such a standard.

It is perhaps only another way of putting the same thing to say that law has developed and is developing constantly by reference to the pursuit of ends more or less consciously arrived at by mankind.  So far as these ends are common, and I take it that in the main, amid national and individual diversity and conflict they are common ends, law has been formed for their attainment.  On the whole what men have asked law to do for them has been the same at any given stage in civilization.  The eighteenth century asked for liberty, property, and happiness.  We are putting a rather different meaning, or perhaps a different stress on the words, not only here but throughout the civilized world, and the main movements of legal change are in the same direction everywhere.

One word about the two kinds of law known as Public and Private International law.

The fact that the laws of different countries are different gives rise to problems whenever the Courts of one country have to deal with a set of facts where some foreign element is involved, for instance a citizen or an inhabitant of another country, or property which is in another country, or a contract or transaction which took place abroad.  Now we have long got past the stage at which the Courts could simply disregard the foreign element, could say this man is a foreigner, therefore he has no rights; or this event took place abroad, and therefore we will treat it as if it had never happened.  On the other hand it will not do for the Court to apply simply its own law.  Grave injustice would be done, for instance, if a transaction made on the faith of law which will give a certain effect to it, were treated as made under another law which will give it a different effect or no effect at all.  For this reason the Courts of every country have formed rules (sometimes called Private International Law; sometimes, and as some hold, more properly, called ‘Conflict of Laws’) by which they determine how far, where a foreign element is involved, the foreign law is to be carried out rather than the law which the Court applies in ordinary cases.  These rules are not the same in every country, because differences of opinion are possible as to what justice requires.  But the very existence of such rules shows that the Courts hold that the world of law is one, however much diversified, and that no one territorial law can blindly go on its way without taking account of its neighbours.