What beans means to a medieval priest

As parents brought their children to him for baptism, a particular Florentine priest would store one black bean for each boy and one white bean for each girl. This was in the first half of the 14th century, and (as the chronicler Giovanni Villani tells us) the beans numbered annually between 5,500 and 6,000, "with the male sex most times surpassing the female by 300 to 500 each year". Far in advance of the modern governmental census, it would appear that medieval Tuscans had some interest in measuring demographic trends.

A warning to the casual browser: The Measure of Multitude is not a socioeconomic study of population. While one will learn from it about the expansion of the European populace in the 12th and 13th centuries, which some historians have seen as leading to a disastrous overpopulation in the following century, Peter Biller is not primarily interested in 14th-century famine and plague. Rather he is concerned with how medieval people thought about population. Or perhaps one should say, how, when and why certain medieval writers came to think about what we would now call "demographic" questions: population size, male-female ratio, birth-death ratio and so forth.

The contexts behind these thoughts are fascinating: William of Auvergne, writing in the early 13th century, thinking about the fact of apparently licit polygamy in the Old Testament, suggested that there must have been a gender imbalance - more women than men, hence too few husbands, hence God permitting polygamy. This led to consideration of whether such an imbalance was possible or desirable, and other effects it might have.

Using an astounding range of material, Biller brings these contexts to light, and traces how ways of thinking about demography in the Middle Ages developed and what some of their implications were. We are led through subjects including medieval ideas about marriage, procreation, contraception, virginity, the common good, perceptions of Islam, and the social and intellectual contexts of pastoral care manuals, to mention but a few.

The book covers most of Europe both geographically and socially. There is, however, an overall thesis: that over the course of the 12th century medieval writers developed ways of thinking and writing about "demographic" questions, and that these were then partly shaped by intellectual tradition (shifted in particular directions by the influences of Peter the Lombard and the 13th-century translations of Aristotle's Politics ) and partly affected by the lived reality of an increasingly populous medieval Europe.

Biller insists, in his analysis of writers such as William of Auvergne and Thomas Aquinas, on balancing the influence of intellectual tradition and innovation against the catalytic effects of the material world in which they lived. These medieval thinkers, he suggests, were no ivory-tower dwellers, but men concerned not only with the pursuit of abstract thought but also the need to shape strategies of pastoral care for the burgeoning populace. William's thoughts about how some men may be less successful than others in fathering children, for example, were influenced by his pastoral work: "We have learnt this same thing from women, not from men's rumours or general opinion" - that is, he has learnt it through hearing confession. This is intellectual history, but a kind of intellectual history that insists upon its social context and social influence. Thus, for example, theological discussion of the precept to "go forth and multiply" is set against evidence of medieval strategies for the avoidance of offspring.

What may appear to be abstract debate ("does a precept from olden times still apply today?") is thus connected to practical and fraught matters (the methods used to avoid procreation).

Some areas of the book may tax the general reader, such as a detailed comparison of different translations of Aristotle's Politics. But the writing is lively, witty and clear. And this is an imaginative text, as Biller makes us feel the richness of his historical context. Introducing the expansion of Florence's city walls, marked on November 28, 1284 by the blessing of the first stone laid, we are reminded of what is now lost to us: "Both the impressions and chat of the ordinary people of either sex who thronged around the blessing of the stone in 1284, and the inner reflective lives of the women whose marriages and bodies have supplied the babies."

There is much to admire here, and little to criticise. But while I am inspired by the way in which thinkers are related to their social contexts, I am less persuaded by the neutral, or even cosy, relationship suggested at points between these authors and the mass of people about whom they wrote.

Were all Paris theologians inspired solely by solicitous care toward the social problems of that city or did elements of power and thoughts of control also inform the theories they explored? As Biller notes in his final pages, when writers begin to talk about people in abstract, demographic terms there is something "rather odd and cold" about their discourse. It would have been interesting to develop this thought further - to consider what operations of power and government a demographic mindset enables.

Ultimately, Biller's heterogeneous interests should inspire a wide readership, including scholars of medieval medicine, population, theological thought, religious practice and canon law.

John H. Arnold is senior lecturer in medieval history, Birkbeck, University of London.