[Sidenote: Political thought in Middle Ages.]

The period of three centuries which forms our theme is the central period of the Middle Ages. Its interests are manifold; but they almost all centre round the great struggle between Empire and Papacy, which gives to mediaeval history an unity conspicuously lacking in more modern times. The history of the Church during these three hundred years is more political than at any other period. In order to understand the reason for this it will be well at the outset to sketch in brief outline the political theories propounded in the Middle Ages on the relations of Church and State. So only can we avoid the inevitable confusion of mind which must result from the use of terms familiar in modern life.

[Sidenote: Unity of world.]

Medieval thought, then, drawing its materials from Roman, Germanic and Christian sources, conceived the Universe as Civitas Dei, the State of God, embracing both heaven and earth, with God as at once the source, the guide and the ultimate goal. Now this Universe contains numerous parts, one of which is composed of mankind; and the destiny of mankind is identified with that of Christendom. Hence it follows that mankind may be described as the Commonwealth of the Human Race; and unity under one law and one government is essential to the attainment of the divine purpose.

[Sidenote: Duality of organisation.]

But this very unity of the whole Universe gives a double aspect to the life of mankind, which has to be spent in this world with a view to its continuation in the next. Thus God has appointed two separate Orders, each complete in its own sphere, the one concerned with the arrangement of affairs for this life, the other charged with the preparation of mankind for the life to come.

[Sidenote: Relations of Church and State.]

But this dualism of allegiance was in direct conflict with the idea of unity. The two separate Orders were distinguished as Sacerdotium and Regnum or Imperium; and the need felt by mediaeval thinkers for reconciling these two in the higher unity of the Civitas Dei began speculations on the relation between the ecclesiastical and the secular spheres.

[Sidenote: Theory of Church party.]

The champions of the former found a reconciliation of the two spheres to consist in the absorption of the secular by the ecclesiastical. The one community into which, by the admission of all, united mankind was gathered, must needs be the Church of God. Of this Christ is the Head. But in order to realise this unity on earth Christ has appointed a representative, the Pope, who is therefore the head of both spheres in this world. But along with this unity it must be allowed that God has sanctioned the separate existence of the secular no less than that of the ecclesiastical dominion. This separation, however, according to the advocates of papal power, did not affect the deposit of authority, but affected merely the manner of its exercise. Spiritual and temporal power in this world alike belonged to the representative of Christ.

[Sidenote: Sinful origin of State.]

But the bolder advocates of ecclesiastical power were ready to explain away the divine sanction of temporal authority. Actually existing states have often originated in violence. Thus the State in its earthly origin may be regarded as the work of human nature as affected by the Fall of Man: like sin itself, it is permitted by God. Consequently it needs the sanction of the Church in order to remove the taint. Hence, at best, the temporal power is subject to the ecclesiastical: it is merely a means for working out the higher purpose entrusted to the Church. Pope Gregory VII goes farther still in depreciation of the temporal power. He declares roundly that it is the work of sin and the devil. "Who does not know," he writes, "that kings and dukes have derived their power from those who, ignoring God, in their blind desire and intolerable presumption have aspired to rule over their equals, that is, men, by pride, plunder, perfidy, murder, in short by every kind of wickedness, at the instigation of the prince of this world, namely, the devil?" But in this he is only re-echoing the teaching of St. Augustine; and he is followed, among other representative writers, by John of Salisbury, the secretary and champion of Thomas Becket, and by Pope Innocent III. To all three there is an instructive contrast between a power divinely conferred and one that has at the best been wrested from God by human importunity.

[Sidenote: Illustration of relations.]

There are two illustrations of the relation between the spiritual and secular powers very common among papal writers. Gregory VII, at the beginning of his reign, compares them to the two eyes in a man's head. But he soon substitutes for this symbol of theoretical equality a comparison to the sun and moon, or to the soul and body, whereby he claims for the spiritual authority, as represented by the soul or the sun, the operative and illuminating power in the world, without and apart from which the temporal authority has no efficacy and scarcely any existence. An illustration equally common, but susceptible of more diverse interpretation, was drawn from the two swords offered to our Lord by His disciples just before the betrayal. It was St. Bernard who, taking up the idea of previous writers that these represented the sword of the flesh and the sword of the spirit respectively, first claimed that they both belonged to the Church, but that, while the latter was wielded immediately by St. Peter's successor, the injunction to the Apostle to put up in its sheath the sword of the flesh which he had drawn in defence of Christ, merely indicated that he was not to handle it himself. Consequently he had entrusted to lay hands this sword which denotes the temporal power. Both swords, however, still belonged to the Pope and typified his universal control. By virtue of his possession of the spiritual sword he can use spiritual means for supervising or correcting all secular acts. But although he should render to Caesar what is Caesar's, yet his material power over the temporal sword also justifies the Pope in intervening in temporal matters when necessity demands. This is the explanation of the much debated Translatio Imperii, the transference of the imperial authority in 800 A.D. from the Greeks to the Franks. It is the Emperor to whom, in the first instance, the Pope has entrusted the secular sword; he is, in feudal phraseology, merely the chief vassal of the Pope. It is the unction and coronation of the Emperor by the Pope which confer the imperial power upon the Emperor Elect. The choice by the German nobles is a papal concession which may be recalled at any time. Hence, if the imperial throne is vacant, if there is a disputed election, or if the reigning Emperor is neglectful of his duties, it is for the Pope to act as guardian or as judge; and, of course, the powers which he can exercise in connection with the Empire he is still more justified in using against any lesser temporal prince.

[Sidenote: Theory of Imperial party.]

To this very thorough presentation of the claims of the ecclesiastical power the partisans of secular authority had only a half-hearted doctrine to oppose. Ever since the days of Pope Gelasius I (492-6), the Church herself had accepted the view of a strict dualism in the organisation of society and, therefore, of the theoretical equality between the ecclesiastical and the secular organs of government. According to this doctrine Sacerdotium and Imperium are independent spheres, each wielding the one of the two swords appropriate to itself, and thus the Emperor no less than the Pope is Vicarius Dei. It is this doctrine behind which the champions of the Empire entrench themselves in their contest with the Papacy. It was asserted by the Emperors themselves, notably by Frederick I and Frederick II, and it has been enshrined in the writings of Dante.

[Sidenote: Its weakness.]

The weak point of this theory was that it was rather a thesis for academic debate than a rallying cry for the field of battle. Popular contests are for victory, not for delimitation of territory. And its weakness was apparent in this, that while the thorough-going partisans of the Church allowed to the Emperor practically no power except such as he obtained by concession of or delegation from the Church, the imperial theory granted to the ecclesiastical representative at least an authority and independence equal to those claimed for itself, and readily admitted that of the two powers the Church could claim the greater respect as being entrusted with the conduct of matters that were of more permanent importance.

Moreover, historical facts contradicted this idea of equality of powers. The Church through her representatives often interfered with decisive effect in the election and the rejection of secular potentates up to the Emperor himself: she claimed that princes were as much subject to her jurisdiction as other laymen, and she did not hesitate to make good that claim even to the excommunication of a refractory ruler and -- its corollary -- the release of his subjects from their oath of allegiance. Finally, the Church awoke a responsive echo in the hearts of all those liable to oppression or injustice, when she asserted a right of interposing in purely secular matters for the sake of shielding them from wrong; while she met a real need of the age in her exaltation of the papal power as the general referee in all cases of difficult or doubtful jurisdiction.

Thus the claims of each power as against the other were not at all commensurate. For while the imperialists would agree that there was a wide sphere of ecclesiastical rule with which the Emperor had no concern at all, it was held by the papalists that there was nothing done by the Emperor in any capacity which it was not within the competence of the Pope to supervise.