62 Law and Morality Abroad (to ca. ad 1550)between po liti cal entities. It was primarily about the conduct of ordinary
persons in everyday life. Natural law was, however, relevant to international
relations, in that rulers were legally bound to observe its rules in their deal-
ings with one another, just as ordinary people were in their everyday lives. If
international law is to be seen, therefore, as a law specifi cally applicable to
the relations of sovereigns and states with one another, then it must be con-
cluded t hat t he Eu ro pe an Midd le Ages k new no such law. But it must equa lly
be emphasized that the Middle Ages certainly did regard rulers as acting
under legal constraints in their mutual relations. It is just that the contents
of those constraints did not diff er from those that were applicable to ordi-
nary folk.
In several respects, the shift from an organicist to a rationalist version of
natural law had some unsettling consequences. One was the impact on the
principle of the natural sociability of humans. It will be recalled that, to Ar-
istotle, sociability was a “natural impulse” of humans— hardwired into the
human biogram. It was automatically and inescapably part of the human
condition. Under the rationalist scheme, however, that confi dence was in
danger of being lost. Aquinas salvaged it as best he could by simply positing
that the rules of natural law are compatible with “our natural inclinations”—
and that among these is “a natural inclination... to live in society” and “to
avoid giving off ence to those among whom one has to live.” Natural- law
thought, therefore, even in its newer rationalist form, managed to retain the
traditional commitment to the principle of the natural sociability of hu-
mankind. Th e world is, in this picture, fundamentally harmonious and
orderly rather than chaotic and violent.
Th is alliance between natural- law thought and the principle of intrinsic
human sociability would continue to be a very solid one— to a large extent
enduring to the present day. It should be appreciated, though, that the two
are not really logically connected. Th is point would be demonstrated in the
seventeenth century by Th omas Hobbes, who accepted natural law while
brazenly discarding natural sociability. Hobbes, though, was one of na-
ture’s great contrarians. For the overwhelming part, natural law and natural
sociability traveled, at least de facto, in close harness.
Another disturbing eff ect of the shift from an organicist to a rationalist
picture of natural law was the implication that it had on the ius gentium.
Th e old idea of Ulpian, that natural law applied to the whole of the animal