26 Law and Morality Abroad (to ca. ad 1550)It is well, at this point, to take note of another of Aristotle’s ideas that
similarly would go on to play a very great role in international legal thought.
Th is was the notion of the natural sociability of humans. Similarly to Men-
cius, Aristotle held that there is “a natural impulse” among humans toward
cooperation. More specifi cally, this natural impulse leads humans to one
par tic u lar form of cooperation: the (Greek) city- state. It is in this specifi c
sense that Aristotle’s famous statement of humans as “po liti cal animals”—
that is, as animals naturally inclined toward life in a polis setting— must be
understood. Th is natural sociability, however, had a distinctly limited
reach. It went as far as the polis, but no farther. All politics are local, it is
sometimes said— a sentiment that is far from new.
Aristotle’s theory of the state did not have any ineluctable implications for
the problem of relations between states. Each state was in de pen dent of all
others, to be sure. But what, if anything, prevented man’s “natural impulse”
to cooperation from manifesting itself at this higher level, too? Aristotle’s
po liti cal theory was eff ectively neutral on this question. Th e in de pen dent
states might be disposed to be cooperative and friendly toward one another,
or they might be engaged in perpetual warfare, or any combination of these.
Th e furthest that we can safely go here is to conclude that Aristotle, armed
with his principle of the natural sociability of humans, at least allowed for
the possibility of a generally harmonious interstate system.
Prevailing opinion within the Greek world, so far as it can be discerned
from a vast historical distance, was divided on this question. Th ere certainly
was at least some belief that relations between states were intrinsically hos-
tile. A speaker in one of Plato’s dialogues referred to a general belief that
states “are all engaged in a never- ending lifelong war against all other states.”
As a result, “what most men call ‘peace’ is really only a fi ction, and in cold
fact all states are by nature fi ghting an undeclared war against every other
state.” No explicit doctrine of just wars was ever devised by the Greeks,
although Aristotle did concede that it was “quite possible” that a war might
be waged without a just cause. But he did not elaborate on this potentially
interesting point.
It should also be appreciated, though, that the Greek ethic of resolute in-
de pen dence of city- states from one another was counterbalanced, to at least
some extent, by a palpable consciousness of cultural unity within the Greek
world. In words attributed by the historian Herodotus to offi cials of Athens,