10 Law and Morality Abroad (to ca. ad 1550)applied to wars on the largest of scales as well as on the smallest. When Alex-
ander the Great embarked on his epic conquest of the Persian Empire (and
beyond) in the fourth century bc, he went armed with a legal justifi cation, in
addition to his troops and weapons. He was, at least ostensibly, avenging the
Persian invasion of Greece of a century and a half earlier. Th ere was no short-
age of skepticism as to the validity of this justifi cation. But the crucial point is
that it was generally seen to be necessary for even the greatest of conquerors to
have justice on their side, as well as the god of battles.
How this general feeling came to take hold, and to be so widely held, is
shrouded in mystery to the present day. Some have asserted the existence of
a universal and biologically innate sense of justice in humans, analogous to
the universal religious sensibility posited by some anthropologists. Certain
schools of thought about natural law have been, and continue to be, based
on this thesis. Th ese claims of a universal consciousness of justice—“written
in the hearts of men,” as sometimes asserted— may well be true. But it is also
likely to have been true that this innate instinct of justice has required the
presence of certain social, economic, po liti cal, and religious conditions to
fl ourish to its fullest extent.
It seems likely that, in the beginning, this sense of justice had free play
only within very limited bounds— that it began at home and then gradually
spread outward, fi rst to relatives (sometimes of fairly great biological dis-
tance), then to nonrelated near neighbors, then to more distant persons, and
eventually encompassing, say, a city- state or a sizable region. Th ere appears
to be no à priori reason that the pro cess could not extend more widely, to
operate within large nation- states, or even multinational empires. It might
even expand further yet— to apply to relations between these larger entities.
To this last step, we have come to attach the name “international law.” Our
ancient ancestors did not apply that label, but they did achieve something of
major importance. Th ey applied, in their practice, the germ of the idea. And
from that germ, there grew the idea itself. But not everywhere. In fact, it was
only in the civilizations at the far western end of the Eurasian land mass that
general ideas of an impersonal and transnational system of justice took any-
thing like deep roots.