bius, _Vita Constantini_, lib. iv, cap. xxiv.

[2] Theodosius II, _Novellae_, tit. iii (438).

The Middle Ages inherited these views. Religious unity was then
attained throughout Europe. Any attempt to break it was an attack at
once upon the Church and the Empire. "The enemies of the Cross of
Christ and those who deny the Christian faith," says Pedro II, of
Aragon, "are also our enemies, and the public enemies of our kingdom;
they must be treated as such."[1] It was in virtue of the same
principle that Frederic II punished heretics as criminals according
to the common law; _ut crimina publica_. He speaks of the
"Ecclesiastical peace" as of old the emperors spoke of the "Roman
peace." As Emperor, he considered it his duty "to preserve and to
maintain it," and woe betide the one who dared disturb it. Feeling
himself invested with both human and divine authority, he enacted the
severest laws possible against heresy. What therefore might have
remained merely a threatening theory became a terrible reality. The
laws of 1224, 1231, 1238, and 1239 prove that both princes and people
considered the stake a fitting penalty for heresy.

[3] Law of 1197, in De Marca, _Marca Hispanica_, col. 1384.

It would leave been very surprising if the Church, menaced as she was
by an ever-increasing flood of heresy, had not accepted the State's
eager offer of protection. She had always professed a horror for
bloodshed. But as long as she was not acting directly, and the State
undertook to shed in its own name the blood of wicked men, she began
to consider solely the benefits that would accrue to her from the
enforcement of the civil laws. Besides, by classing heresy with
treason, she herself had laid down the premises of the State's
logical conclusion, the death penalty. The Church, therefore, could
hardly call in question the justice of the imperial laws, without in
a measure going against the principles she herself had advocated.

Church and State, therefore, continually influenced one the other.
The theology upheld by the Church reacted on the State and caused it
to adopt violent measures, while the State in turn compelled the
Church to approve its use of force, although such an attitude was
opposed to the spirit of early Christianity.

The theologians and the canonists put the finishing touches to the
situation. Influenced by what was happening around them, their one
aim was to defend the laws of their day. This is clearly seen, if we