In 1966 Keith Thomas wrote an article in the Times Literary Supplement which laid down the axiom, ‘All historical propositions relating to the behaviour of large groups, for example… religious activity, are susceptible of treatment in this [statistical] way, and indeed permit of no other.’ Social historians have increasingly adopted this approach ever since. It has obviously great merits: I am sometimes afraid, indeed, that the principle is in some ways not being carried far enough, and that only the letter, and not the law, is being implemented. For instance, in my own field, individual village studies, often of high quality, are produced. But their authors frequently omit to indicate the nature of the agricultural and marketing region in which their community lies, and therefore fail to establish either its probable social structure or its ‘normality’ or ‘abnormality’ within its area. Quantified studies of great complexity and considerable value are therefore produced; but this value is diminished by the total ignorance of the reader, and sometimes it seems of the author, of the ‘typicality’ of the example.

Uncertainty regarding the circumstances in which devotion to the image of the Virgin of Guadalupe was established is almost as old as the devotion itself. The earliest surviving version of the legend, which recounts the adventures of the celebrated statue from the time of Gregory the Great to its discovery in the Montes de Toledo by the pastor Gil Cordero - an account dating from the late fourteenth or early fifteenth century - places its reappearance in the reign of the son of Fernando iii of Castile, ‘su fijo Don Alfonso el qual gano las Algesiras e murio sobre Gibraltar’, thus conflating Alfonso x, Fernando iii's son, who died in 1284, with Alfonso x's great-grandson Alfonso xi (1312–50). Attempts to unscramble or to disguise this confusion have a long history too, the earliest being that of the corrector of Ms AHN 48B, who expunged words and phrases and supplied marginal additions to bridge the gap between the reigns of the two Alfonsos.

On 25 May 1085 Pope Gregory VII died in exile. The ninth centenary of the death of this great pope – ‘the greatest who has ever sat in St. Peter's chair’ Erich Caspar called him in 1924 – provides an obvious pretext for a bibliographical essay. What makes such. an essay a necessary exercise rather than a mere commemorative gesture is the fact that there is not available at present in any language a full-scale biography of Hildebrand–Gregory which reflects the current state of research. There is no doubt that Gregorian studies are flourishing: the colloquium in Salerno in May 1985 will offer an impressive account of research in progress. Over 200 books and articles on different aspects of the life and thought of Hildebrand-Gregory, written in the second half of this century, are listed below. Perhaps it is this sheer wealth of material and opinion which has disheartened potential biographers. The following survey concentrates on Gregorian literature since 1947, the year in which the Salesian and Scriptor of the Vatican Library, Father Giovanni Battista Borino (1881–1966) founded in Rome the journal Studi Gregoriani, which has certainly fulfilled its founder's purpose of stimulating research into the history of the papal reform movement.