he Christian principle itself, which made for the dominance of the idea
of unity in mediaeval thought.

Before we proceed to draw another negative conclusion from the principle
of the one community, we must enter a brief caveat in regard to the
conclusion which has just been drawn. We cannot altogether take away the
State from the Middle Ages by a stroke of the pen and the sweep of a
paradox. There were states in mediaeval Europe, and there were kings who
claimed and exercised _imperium_. These things caused the theorists, and
particularly the Roman lawyers, no little trouble. It was difficult to
reconcile the unity of the _imperium_ with the multiplicity of kings.
Some had recourse to the theory of delegation, and this seems to be the
theory of the _De Monarchia_ of Dante. But there was one contemporary of
Dante who said a wise thing, prophetic of the future. _Rex est in regno
suo_, wrote Bartolus of Sassoferrato, _imperator regni sui_. In that
sentence we may hear the cracking of the Middle Ages. When kings become
'entire emperors of their realms' (the phrase was used in England by
Richard II, and the imperial style was affected by Henry VIII), unity
soon prepares to fly out of the window. But she never entirely took
flight until the Reformation shattered the fabric of the Church, and
made kings into popes as well as emperors in their dominions.

We may now turn to draw another conclusion from the mediaeval principle
of unity. To-day the world recognizes, and has recognized for nearly
four centuries, not only a distinction between States, but also a
distinction between two societies in each State--the secular and the
religious. These two societies may have different laws (for instance, in
the matter of marriage), and conflicts of duties and of jurisdictions
may easily arise in consequence. The State may permit what the Church
forbids; and in that case the citizen who is also a churchman must
necessarily revolt against one or other of the societies to which he
belongs. The conflict between the two societies and the different
obligations which they impose was a conflict unknown to the Middle Ages.
Kings might indeed be excommunicated, and in that event their subjects
would be compelled to decide whether they should disobey excommunicated
king or excommunicating pope. But that was only a conflict between two
different allegiances to two different authorities; it was not a
conflict between two different memberships of two