Church and state in medieval Europe

[1] Emperor Constantine issued the Edict of Milan in 313 proclaiming toleration for the Christian religion, and convoked the First Council of Nicaea in 325 whose Nicene Creed included belief in "one, holy, catholic, and apostolic Church".

[2] Pope Leo the Great defined the role of the state as being a defender of the church's cause and a suppressor of heresies in a letter to the Eastern Roman Emperor Leo I: "You ought unhesitatingly to recognize that the Royal Power has been conferred to you not only for the Rule of the world, but especially for the defense of the Church, so that by suppressing the heinous undertakings you may defend those Statutes which are good and restore True Peace to those things which have been disordered".

The last group, though small in number, monopolized the instruments and opportunities of culture, and ruled with almost unlimited sway half of the most powerful continent on the globe.

The clergy, like Plato's guardians, were placed in authority... by their talent as shown in ecclesiastical studies and administration, by their disposition to a life of meditation and simplicity, and ... by the influence of their relatives with the powers of state and church.

In the latter half of the period in which they ruled [800 AD onwards], the clergy were as free from family cares as even Plato could desire [for such guardians]... [Clerical] Celibacy was part of the psychological structure of the power of the clergy; for on the one hand they were unimpeded by the narrowing egoism of the family, and on the other their apparent superiority to the call of the flesh added to the awe in which lay sinners held them....

The conflict between Church and state was in many ways a uniquely Western phenomenon originating in Late Antiquity (see Saint Augustine's City of God (417)).

Hence, absolutism was made possible by new innovations and characterized as a phenomenon of Early Modern Europe, rather than that of the Middle Ages, where the clergy and nobility counterbalanced as a result of mutual rivalry.

A dispute between the secular and ecclesiastical powers emerged known as the Investiture Controversy, beginning in the mid-eleventh century and was resolved with the Concordat of Worms in 1122.

While on the surface it was over a matter of official procedures regarding the appointments of offices, underneath was a powerful struggle for control over who held ultimate authority, the King or the Pope.

However the King reneged on his promises made at Fréteval and in response Becket produced a number of censures on royal officials and clergymen.

Guelf (also spelled Guelph) and Ghibelline, were members of two opposing factions in German and Italian politics during the Middle Ages.