to enforce
a legal and peaceful attitude in its own individual citizens towards
each other. The state is the guardian of its citizens' peace, but the
old problem recurs: _Quis custodiet ipsos custodes?_

It is obvious that this difficulty increases as the size of states
increases. To compel a small state to keep the peace by absorbing it if
it fails to do so is always an easy and even tempting process to a
neighbouring larger state. This process was once carried out on a
complete scale, when practically the whole known world was brought under
the sway of Rome. "War has ceased," Plutarch was able to declare in the
days of the Roman Empire, and, though himself an enthusiastic Greek, he
was unbounded in his admiration of the beneficence of the majestic _Pax
Romana_, and never tempted by any narrow spirit of patriotism to desire
the restoration of his own country's glories. But the Roman organization
broke up, and no single state will ever be strong enough to restore it.

Any attempt to establish orderly legal relationships between states
must, therefore, be carried out by the harmonious co-operation of those
states. At the end of the sixteenth century a great French statesman,
Sully, inspired Henry IV with a scheme of a Council of Confederated
European Christian States; each of these states, fifteen in number, was
to send four representatives to the Council, which was to sit at Metz or
Cologne and regulate the differences between the constituent states of
the Confederation. The army of the Confederation was to be maintained in
common, and used chiefly to keep the peace, to prevent one sovereign
from interfering with any other, and also, if necessary, to repel
invasion of barbarians from without. The scheme was arranged in concert
with Queen Elizabeth, and twelve of the fifteen Powers had already
promised their active co-operation when the assassination of Henry
destroyed the whole plan. Such a Confederation was easier to arrange
then than it is now, but probably it was more difficult to maintain, and
it can scarcely be said that at that date the times were ripe for so
advanced a scheme.[224]

To-day the interests of small states are so closely identified with
peace that it is seldom difficult to exert pressure on them to maintain
it. It is quite another matter with the large states. The fact that
during the past half century so much has been done by the larger states
to aid the cause of international arbitration, and to