nations arose.]

3. The idea of an international community of law could not have obtained
acceptance before a time when there existed a number of completely
independent states, internally akin in virtue of a community of
intensive civilization and continually brought into contact with one
another by a lively intercourse. It was in this way that an
international community of law was begotten at the end of the middle
ages out of Christian civilization and mutual intercourse. Grotius and
his forerunners would not have been able to create international law,
had not the conception of a community of law between Christian states
enjoyed a general recognition, and had not international intercourse
before their day evolved already a large number of rules of intercourse,
which were based on custom and in part on very ancient usages.

[Sidenote: The law of nature as the basis of the law of nations.]

4. A theoretical basis for the erection of a system of international law
was provided by the law of nature. This likewise is duteously traced
back by science to Grotius, although in this department also he stands
on the shoulders of his predecessors. The riddle, how it was possible to
find a foundation for international law (as also for constitutional law
and other branches of law) in the law of nature, which itself reposed
upon so unstable a basis, is easy of solution for those who contemplate
the historical development of all law with minds clear from prejudice.
The contention of the historical school that all law springs up
'naturally', like language, is chimerical. Wherever a demand for law and
order imperiously asserts itself, rules of law arise there. Every epoch
of history produces alike that mode of legal development which it needs
and that theoretical basis therefor which corresponds to its own
interpretation of the nature of things. Accordingly the growth of law is
everywhere dependent on, or at least influenced by, a conscious or
unconscious creation of law. Custom, usage, habit, religion, morality,
the nature of the thing, tradition, reason, the examples of single
individuals, and many other factors, contribute the material out of
which the requisite rules of law are built up. Where a strong central
authority busies itself, year in year out, with legislation, expressly
enacted law naturally takes the foremost place, and customary law makes
itself felt to a less and less degree. But where such a strong central
authorit