Much of the shape of modern Europe was determined by changes which took place in the time of Gregory VII, who as 'Hildebrand' was a powerful influence in the papacy from 1046 and was himself pope from 1073 to his death 1085. Because Gregory and his ideas played an important role in many of the changes, a knowledge of his pontificate is essential for understanding later European history, up to and including the present.

Gregory has not lacked historians, from his own time onwards. Among the pregnant changes of his time was a shift from speech towards writing as the principal means of government communication and record. Mainly as a result, Gregory's pontificate was covered by a burst of contemporary documentation. He left a Register (office copies of his outgoing official correspondence in the form of 360 letters), which stands in the Vatican Archive as Registrum Vaticanum 2, - R.V. 1 being the register of John VIII (872-82) two centuries before. Since Gregory VII's policies also sparked off widespread disputes conducted, to a degree none had been since the fourth century, by written appeals to literate opinion, we also possess thr ee printed volumes of polemical pamphlets (or libelli), while ordinary historiography was also on the increase in his time, given extra stimulus by his ideas the reactions to them; so there was also a new spate of chronicles.

This cache of documentation has fed a corpus of modern historiography, fired by an interest in the same issues, which endure (their endurance actually constitutes one of the permanent changes in our culture the Gregorian movement brough t about). The fifty years before the First World War gave birth to three Life-and-Times biographies, the shortest with two volumes, the longest with seven. Between the Wars Augustin Fliche added his three-volume La Réforme Grégorienne (1926-37) and H.-X. Arquillière his one-volume essay Saint Grégoire VII (1934), - to say nothing of the handy English introduction by A. J. Macdonald, Hildebrand (1932). All that time, and more copiously since, a stream of periodical and Festschrift articles has kept the scholarly world informed, augmented from 1947 by an irregularly appearing periodical entirely devoted to Gregory VII, Studi Gregoriani.

Despite this continued historiography, since the 1930s there has been no major monograph to gather together new knowledge and new points of view. The present volume fills that need. Its author, the Reverend H. E. J. Cowdrey, is amon g the two or three living scholars mostly qualified to write it, his publications in the field having begun thirty years ago and remained standard. In 1972 he edited the sixty or so Gregorian letters to survive outside the Vatican Register. In 1970 his The Cluniacs and the Gregorian Reform had explored one important facet of Gregory's movement, and in 1983 he addressed another in The Age of Abbot Desiderius. In the same period he has contributed more than thirty articles on the Gregorian reform as it impinged on particular countries, groups, or contemporary ideas (many of the articles now collected in volumes). The appearance of his Gregory VII is therefore itself a historical event, likely to establish a canon for m any years ahead.

Its text of 627 pages takes the reader patiently through the primary evidence on Hildebrand's birth (c. 1015) and younger years, and then, in the ten central chapters, on Gregory VII's twelve years as pope. These ten chapters fall into two groups. One rehearses Gregory's dealings with successive territorial powers: Germany (given a monster chapter of its own, of 200 pages), Italy, France, and, more briefly, countries round the edge of Latin Europe, including Spain and Anglo-N orman England, these being followed in a separate chapter by the eastern churches and Islam. A second group, of four chapters, then examines the pope's attitudes in successive conceptual areas: the religious and moral foundations of his thought, his ide as on church order, on the relation of priesthood and kingship, and on monasticism. Two very short chapters make a coda with an account of Gregory's death, and a general assessment.

The prodigious industry embodied in a book of this rank normally demands a modicum of the same from its reader, and this one, true to the rule, makes a substantial read, at times reminiscent of the experience of going through file after file in an office. Indeed that is what much of it is. Gregory's 360-plus-60 known letters are scrutinized and compared with related sources, in relation to each event; and then, in many cases, scrutinized and compared again in the later chapters with t heir relevant conceptual questions in mind. What drives the reader on is not only the intrinsic interest of the subject-matter but admiration for the book's all-but-perfect degree of organization (my only cavils in that area are the meanness of the ind ex in relation to the wealth of material hidden in the book, and the author's sectional system of cross-references - editor-friendly, reader-unfriendly). This thorough re-examination of the sources will leave even Gregory aficionados abuzz with new ideas .

The aficionados will also, naturally, spot omissions and points of difference. One challenge of historical writing is that the number of omissions in a book will be proportional to its length (for the same reason that a big empire has a long frontier to defend). Thus Cowdrey's absorption in the documents is such that he does not reflect more than fleetingly on the nature of his principal document, namely the Register, and what that tells us about the character of papal government. Nor is Cowdrey any partisan for the soci-economic school. He touches lightly on the Roman Jew Baric († c. 1016), who became a Christian and sired the Purlin dynasty with its two popes; but too lightly to get us speculating on what a wealthy Jew was doing in Rome then: whether his presence, that is, had anything to do with an incipient Roman commercial revolution, of the kind that more generally lay behind the spread of simony (the commercialization of church office), the reformers principal enem y, as it transformed the relationship between towns and their bishops (as indeed between nations and their kings). Again, when Philip I of France was accused by Gregory of 'robbing' Italian merchants (who no doubt told the tale to Gregory), Cowdrey repea ts the charge without pausing to ask if this incident was not just an explosive announcement of the arrival en scène of the Champagne fairs and of the Capetians' felicitous discovery of the device of charging tolls.

There is a measure of vacuum, then, on economic matters. On social, it can be no coincidence that two of the least convincing of Cowdrey's judgements touch this area. One is Hildebrand's birth. In the past, much has been made of an e xpression used by a friendly ecclesiastic, that God had chosen Hildebrand 'de plebe sua'. But that only meant Hildebrand was like King David (cf. Ps. 88:20), not that he was of what we might call 'plebeian' birth; a conclusion rendered even less likely by young Hildebrand's having an avunculus (mother's brother) as abbot of Rome's most prestigious monastery. A second questionable area touches that central subject of moral reform: clerical celibacy. Cowdrey, like Gregory, reads clerical celibacy a s church rule of uncontestable age and authority, approved (Cowdrey writes) by 'almost everyone who, in the second half of the eleventh century, was concerned with the condition of the church.' Literally hundreds of German and Italian clergy would have contested that. One consequence of that simple equation is any priest who thought himself respectably married St Peter Damian's father, for instance) becomes simply a 'fornicator', a term repeated by Cowdrey, as by Gregory, as if neither psychology nor law ever admitted honest doubt. However much we may back the reformer's stand on celibacy we do not have to make that mistake. (One of the many paradoxes of Gregory's life is that the apostle from he drew his authority, St Peter, had been a married m an.)

Aficionados will therefore find points to pick at if they want. Prudent ones, however, will not want to; because they will see that they might, by doing so, risk walking past the value of the book as a whole. It is, in fact, a pe arl of great price. What the reader gets for his modicum of industry is a picture of finer resolution than any other available, or indeed that could be available without Cowdrey's patient method and acquaintance with secondary scholarship. The outcome i s like a magnified scientific photograph, which reveals at a glance the lineaments of an otherwise mysterious and invisible natural process.

Summary cannot do justice to that picture, but can sketch its outline. Gregory must have had a coherent philosophy, we imagine, otherwise he could not have shaken the world. Cowdrey's shows this to be wrong, and proves, rather, Greg ory's remarkable degree of flexibility, at times even uncertainty. We may protest, what about the lofty certainties of the so-called Dictatus papae (a series of 27 propositions, exalting papal authority, found in Gregory's Register between two lett ers dated in March 1075)? Cowdrey shows they were of little or no account. Whatever the origin of the list, Gregory subsequently ignored it, and it can represent no more than a record of one stage in Gregory's private thinking as his crisis developed. Again, we may ask, what about the Donation of Constantine (an eight-century forgery purporting to convey from that Emperor to the bishop of Rome ex officio, imperial authority over Rome and other ill-defined 'parts of the West')? Gregory ignored that too. At least, he never quoted it or referred to it, and built up his claims on other grounds. Even Gregory's often-mentioned claims to hold suzerainty of certain kingdoms by 'feudal' right are revealed, through a careful array of all related utt erances, as too awash with inconsistencies to qualify as coherent political legal doctrine.

The one thing demonstrably consistent in Gregory, to put over against that flexibility, was religious faith: a faith fed (to follow the testimony of Guido of Ferrara, otherwise a strong critic) by constant prayer, the reading of the Bi ble (which Gregory knew well and often quoted, Jeremiah and the Pauline epistles being prominent), and daily Mass, celebrated (Guido wrote) 'with tears in his eyes'. Like the faith of Gregory VII's model, Gregory the Great, this was a faith diffusivum sui, self-diffusing. Not only was the pope generous with time and care for people with problems ('No one ever went empty away who approached him for a hearing', according to the same Guido). Where Gregory the Great had diffused his faith largely by p reaching and dispatching missionaries, Gregory VII sought to reactivate the church as a structure, which he saw currently sunk into near-identity with secular society. The salt had lost its savour. Central to this restoration project was Christ's commis sion to St Peter, whose duty and authority to 'feed my sheep' Gregory VII understood as passing to all bishops of Rome. (As a Roman, we may add, Gregory would have been more than ever attached to St Peter because of the age-old bond which held every Itali an city to its saintly patron). Gregory believed he was the vicar of St Peter on earth, if not yet, quite, in any official writings at least, vicar directly of Christ (a papal title only permanently established from Innocent III's time).

Faith, in that form, was what was fixed in Gregory's thought. Everything else was accessory, and open to modification. Cowdrey's file-by-file analysis demonstrates this first in respect of the articles of church reform. Take lay invest iture (the practice by which a layman formally appointed someone to church office), which proved the most contentious. Lay investiture was general when Gregory became pope and it is well known that Gregory only came to tackle it only by steps. But how many steps? More that we thought. Cowdrey explains how Gregory was not persuaded to cross the Rubicon of lay investiture by its long-standing critic, the radical Humbert of Silva Candida. Rather it was an incident in 1074, when one of two bishops King He nry IV was then investing, the canonically-minded Anselm II of Lucca, took an isolated stand against the procedure. Anselm's stand precipitated Gregory's, and it was Anselm, probably, who brought to Gregory's attention the canon which underpinned this pos ition - a canon, paradoxically, from a council whose authority Gregory would not have recognized had he not been under the illusion that Pope Hadrian II had presided, namely the fourth council of Constantinople, in 869-70. The 22nd canon of that council had banned any lay participation whatever in the appointment of bishops, unless - it added - it was by the churchmen's invitation and in some way they thought appropriate. That canon, from what we think of as Caesaropapist Byzantium, not only toughened t he Gregory's stance against lay investiture but helped him anticipate the provision in which following generations would find a compromise: that a layman could invest a bishop with his temporalities, though not his ecclesiastical office. We associ ate that provision with the canonist Ivo of Chartres, c. 1100, but Cowdrey shows it was employed already in 1078, in the appointment of a bishop of Augsburg.

Gregory's pragmatism in other aspects of the lay-clerical relationship is well known, but not its extent. The pragmatism is shown here by an abundance of example - of Gregory's exhortations to lay congregations to boycott the Masses of incelibate priests; and to princes, to coerce lazy bishops. Anyone doubting Gregory's capacity for tactical somersaults in the matter of clerical and secular spheres of activity can turn to a letter of 1074, suggesting that Gregory, as pope, lead an army to rescue Byzantium from the Turks, and the king is to look after the Roman church while the pope is away.

A pope so reliant on allies had no choice but such ideological gymnastics; nor should it need saying - though it does, and Cowdrey again says it with a new degree of authority - that Gregory was not the only one to shift his positions. Again and again we see a bishop, abbot, prince, or king, shifting a position in response to his own shifting configuration of interests and beliefs, several bishops, for instance, travelling to Rome to see Gregory and being won over, or (though less oft en) repelled, by Gregory's personality. Some of these churchmen had or acquired a vision of their own, similar or all but identical to Gregory's. That indeed is what made the reform movement possible. Examples are the formidable legate Hugh of Lyon, or Wi lliam of Hirsau (a convert to Gregory's viewpoint), and a whole phalanx of Augustinian canons whose pens and tongues laboured for the reform movement in southern Germany (one of them Paul Bernried, Gregory's biographer).

Of men of vision whose vision jarred with Gregory's, the most important was of course Henry IV. Although Cowdrey's book is not about Henry, the king is inevitably portrayed in it and portrayed, like Gregory, as a man dominated by a powe rful central idea, which gained articulation by stages and was expressed in pragmatic policy-shifts. (His appearance as a penitent at Canossa may have been one). This unexpected symmetry between Henry and Gregory makes the book’s most impressive single le sson. While their asymmetries have always been many and obvious, their positions mirrored each other in this, that in each of the pair, in the course of their decade-long confrontation, a single dominant intuition came to isolate itself, and shape and reshape all other policies round it. On Gregory's side, I have mentioned his gradual hardening on the subject of lay investiture, but could have mentioned, as if in recompense, his corresponding softening on clerical celibacy, as the embattled pope s aw that the entire reform movement might founder on an issue so contentious among many clergy (not to mention their wives). Not least - though chronologically last, that is, from the moment when the pope's traditional protector had become his most menacing enemy - Gregory had to find arguments to justify Christian bishops' engagement in war - another canonistic task on which his loyal partisan, Anselm II of Lucca, proved useful.

Corresponding shifts on Henry's side, equally pregnant for the future, included tactical concessions Henry made to political heavyweights whose help he needed. There were royal crowns, on suitable terms, for the rulers of Bohemia and Hu ngary, while the most pregnant of all such concessions were privileges to towns, in Germany but also, more pregnantly still, in Italy, whose independent communes dated their rise from the investiture contest. Tactical concessions apart, deeper shif ts can be found in Henry's policy. The first in time was his sharp awakening to the predicament he had put himself in by encouraging irregularities in the German church. In 1073, German political geometry had been quite different from what it became: then , Cowdrey points out, it had not been the pope but the bishops who had attacked the king as unfit to govern; even to the extent of blaming Gregory for being too friendly to Henry. That all changed, as Henry opened his eyes to where his true challen ge lay and regretted having surrendered the moral high ground to the papalists. By 1075 the game was up for those German careerists who had bought their way into bishoprics and helped finance royal government by doing so, as a wiser Henry embraced r eform, hammering at simony, and granting church privileges as pious any of his forbears' - for instance, to the Hirsau monastic family - and insisted on the payment of tithes to bishops. Given Gregory's ideological twists and turns, Henry even found chanc es to go into the attack as when, late in the pontificate, he told the world Gregory was corrupting Christianity by justifying the church's involvement in war. The most consequential Henrician shift was related to this: the formulation, for the first tim e, of an articulate imperialist doctrine, put out in polemic pamphlets to match and outface the canonists, and anticipating the imperialist theory destined, in the 1150s, to bring into being Barbarossa's 'Holy' Roman Empire, its authority direct from God rather than via the pope.

On both sides, therefore, tactics and the doctrine moved in the course of the dispute, the shifts on one side partly set off by shifts on the other in continuous ricochet - if a ricochet barely perceptible in any picture less finely re solved than this one. The more emphasis the Henricians put on the sacral self-sufficiency of the Empire, the more we find an answering change in Gregory's thought. Following Müller-Mertens, Cowdrey sets out a change in Gregory's phraseology about Henry's kingdom, traceable from 1074, on the basis of an expression known in imperial Italy from c. 1056. As pope, Gregory more and more chose to refer to Henry and his kingdom as 'king[dom] of the Germans', as distinct from saying anything about an Empire. Gregory wanted Germany to be just another kingdom like others, in direct antithesis to the imperialist doctrines now being formulated on the other side. Gregory wanted Germany locked into his preferred world-scheme, in which kings had str ong authority, inheriting their kingdom undivided (he urged the king of Norway not to divide his kingdom between sons), forming a political matrix for the church, but - the big 'but' in Henry's case - not directly involved in its government.

All Gregory demanded of his kings was that they stand up for justitia, which included church autonomy. Because Henry IV had failed on this point, yet remained prima facie the most powerful European monarch, Gregory had to outmanoeuvre him and hence adjust the outlying parts of his own ideology, including a departure, in this one case of Germany, from his usual support for the hereditary principle. Surely without foreseeing the lasting results of what he did, Gregory encour aged the opposite, elective principle in the German royal constitution. Granted the centrifugal forces already present in Germany - between Saxony and the Rhineland, North and South - this intervention tilted the German constitution decisively in a federal direction.

Gregory died in 'exile', in Salerno (Cowdrey argues he was not, as usually supposed, bitter about it, on the ground that it was a kind of blessed martyrdom), while Henry campaigned on, his antipope Clement installed in Rome. Despite the papalists' increasing use of the expression regnum Teutonicorum, the Henrician idea of Empire was far from dead; and when it did finally die, in the reign of Henry's great-great-grandson Frederick II, that would be after a struggle which hurt the papacy almost as much. So Gregory does not look like the winner. In two important respects it was nevertheless Gregory's vision which found vindication by subsequent history. He had forcefully differentiated ecclesiastical from secular power. On one hand that meant that canon lawyers, though they rarely quoted Gregory as an authority (as Cowdrey points out) could in the twelfth century crowd into the curia to build on his bequest, armed after 1130 with an increasingly universal corpus of law, in Gratian' s Decretum, which made the pope rather than any rex Teutonicorum the successor of to the classical Roman Emperor, as supreme appellate authority. Meanwhile, by denying this role to the secular Emperor the post-Gregorian papacy directed western Christendom towards Gregory's, not Henry's, ideal political structure: not, that is, as in the in so many other parts of world, the unified structure of single Empire with direct divine authority, but the fragmented one of states politically independe nt of each other, while sharing the core of a common religion.

Gregory's challenge to Henry and the status quo was compared by a contemporary to an earthquake. Cowdrey's fine-resolution picture - a moving picture, registering subtleties of change - allows the observer to watch the geological processes behind that earthquake, as the elusive tectonic plates creaked into their new positions, in those critical twelve years, to form the foundations of subsequent European politics and culture.