48 Law and Morality Abroad (to ca. ad 1550)arising out of the ius gentium. In this respect, the ius gentium clearly had a
strong private- law fl avor. In addition, though, Hermogenian held that the
ius gentium governed the establishment of public or po liti cal “properties”
(kingdoms and nations), as well as the wars that broke out between them.
Here we have, for the fi rst time, a connection made by a professional lawyer
between the ius gentium and matters that would later be regarded as the
province of international law.
On the basis of these various clues from the Roman jurists, some gen-
eral observations may be safely off ered. Natural law dealt with things in-
stituted by nature itself. It was the set of laws by which the natural world
operated— including universal laws of human behavior such as the forma-
tion of family units and the rearing of children. Humans had no realistic
choice in the adoption or rejection of this set of laws, any more than they
could accept or reject, say, the law of gravity. Th e ius gentium, in contrast,
was a body of law that was invented by humans for their own con ve nience.
It could therefore be added to or altered by human consensus over the
course of time.
Th is twofold legacy of natural law and the ius gentium was Rome’s dis-
tinctive gift to the history of international law. Th ese would go through
many changes in the future (as will be seen in due course). But they would
constitute— even to this day— the very warp and weft of what international
law would become. It is somewhat ironic that the Romans— generally regarded,
with some condescension, as a coarsely practical people— should make their
greatest contribution to international law in the realm of ideas rather than of
practice. For Rome made no striking advances in the everyday techniques of
international law, comparable to, say, the Greek development of interstate
arbitration.
We mu st fi nally note how diff erent were the paths taken by the two great
civilizations at the two ends of Eurasia— China and Rome. In both of these,
there was a certain belief in a global law. But the conceptions were diff ered
radically. Th e Chinese conception of world order was essentially that of a
world state with a single hegemon— the Chinese emperor. Th e Roman vision
was very diff erent. In place of a benevolent universal ruler, it advanced the
more abstract, but ultimately more powerful, idea of an impersonal and
universal rule of law. Moreover, the Roman legacy of universal law, in both
of its incarnations— natural law and the ius gentium— was sharply distin-