In 2015 Fr Augustine Thompson generously agreed to write a history of the Dominican lay brothers (once known as conversi but more recently termed co-operator brothers). A congress of the brothers had met at Lima some two years previously and called for a work that would set out the ‘history, vitality, permanence and presence of cooperator brothers in the life and mission of the Order, including biographies on the Saints, Blessed, and Martyrs, and personal narratives, since its foundation to the present’ (p. ix). A tall order at any time, it was to be written, they hoped, by 2016! That Thompson was able to publish this history in 2017 was no small feat, and the study will no doubt be required reading among Dominicans for many years to come.

In fidelity to his brief, but also constrained by the nature of his sources, Thompson presents within the overarching chronological framework a history that is descriptive, commemorative, and analytical. He charts over six chapters and a short epilogue the main changes that have marked the lives of lay brothers since the Order's pre-history, when St Dominic in 1207 made one Bernard a conversus of the nunnery at Prouille (p. 4). This descriptive history establishes for the reader three distinct periods of very unequal lengths. In the first, which extended from the thirteenth to the eighteenth century, most conversi led a life largely hidden to historians within the friars' monasteries, where they undertook the myriad tasks required for running these often large convents, and formed a distinct body of men segregated in significant respects from their clerical brethren. Governed by their own rule, legislation indicates that the conversi wore a distinct scapular, originally grey, but eventually black (pp. 19–20 and 80); they frequently slept in a separate dormitory, and normally attended their own house chapter (p. 21). Without active or passive voice, they were excluded from decision-making, and subject to a Magister conversorum who was himself a cleric. Often illiterate, and almost always with little or no Latin, the conversi had their own Divine Office, which consisted in reciting a set number of Paters and Aves while attending the choral Office (pp. 25–27). This distinct and subordinate identity was reinforced by the near-impossibility of changing status from conversus to cleric. On the other hand, some conversi might have extensive contact with outsiders: they greeted and screened visitors as porters (p. 49); they begged door-to-door for alms (pp. 45–46); they dealt with enquirers in the sacristy, and as infirmarians might treat the sick in city hospitals (pp. 38–39 and 91–92); they also served as socii to the house's licensed preachers (p. 57). Since the conversi were expected to enter the Order with some skill, and could also be trained by suitably skilled fellow brothers, an exceptional few would shine in specialist crafts that brought them into frequent contact with the wider world as stained-glass makers, civil engineers, and architects (pp. 57–68, and 172–73).

The second period, from the nineteenth to the mid-twentieth century, when many provinces were re-established in the aftermath of revolution and suppression, was marked by much smaller convents in which the specialist skills of lay brothers were no longer required and in which just one or two men largely served as domestics (p. 179). As special skills were not needed, the minimum age of entrants was dropped from twenty-one to seventeen in 1924 (p. 195). The third period, from the mid-twentieth century onwards, has been marked by much greater diversity of work undertaken by better educated entrants, much fraught discussion among the brethren about the necessary formation and status of these co-operator brothers (formally so called since 1958), and by the eventual collapse of previous distinctions between the two types of friar. Thompson draws on extensive archival material, but also on oral history, to detail the different opinions among clerics and among co-operator brothers themselves over recent decades on their place in the Order's life and mission. After the General Chapter of Bogotá in 1965 and the introduction of the new constitutions appended to the acta of the River Forest Chapter in 1968, there was no separate rule for lay brothers, no distinct scapular, no Master of lay brothers, and a new requirement that the brothers would normally attend the choral Divine Office which was now in the vernacular. The lay brothers would enjoy active voice eight years after profession (or six if they entered aged twenty- one or above) and passive voice except for certain offices still reserved to clerics (pp. 229–43). Though Thompson details subsequent minor changes, the River Forest constitutions set the legal framework for the brothers' life which continues to this day.

Alongside this descriptive history, Thompson offers commemorative portraits of holy lay brothers, often drawn from official obituaries. Most are necessarily brief, though he offers more detailed lives of St Martin de Porres - strictly speaking, not a conversus but a professed donatus - and St Juan Macias (pp. 152–59 and 164–67). Thompson also provides an important analysis of the steep decline after 1930 in the number of men offering themselves to the Order as lay brothers. He estimates on the basis of what little evidence we have from the pre-modern era (assignment lists and necrologies) that the likely proportion of lay brothers in the Order from the thirteenth to the late-nineteenth century was typically around 20%, though the proportion varied from house to house and province to province (p. 13). While this percentage remained the much same for period between 1876 and 1930, for which more accurate figures are available, these years also showed much greater diversity between provinces: while lay brothers comprised 38% of friars in the Province of Naples (Provincia Regni, strictly speaking) in 1930, they accounted for only 10% of friars in the Province of France. Between 1930 and 2015 the proportion of lay brothers in the Order dropped to just 5%, some 310 friars (p. 192), while recent vocations are concentrated in a very few entities (provinces in the United States, Poland, and Vietnam). Only nineteen lay brothers remain in the Order who were professed during the 1970s (p. 245). While Thompson does not present figures that would enable us to see what proportion of the drop in numbers was due to a reduced numbers of entrants, as opposed to how many subsequently left, his picture makes clear first that numerical decline had sent in long before the Second Vatican Council or the changes made by General Chapters in the 1960s. Secondly, he shows that those changes, often made in an attempt to halt this decline and welcomed by the existing brothers, were in the short-term at least, wholly ineffectual. Thirdly, he plausibly suggests that in many places the rise in mass-education after World War II meant that a larger proportion of young Catholic men were able to choose a clerical vocation than previously, some of whom might otherwise have offered themselves as lay brothers (pp. 202–203). Fourthly, his research into current opinion suggests that the question of whether lay brothers can serve as superiors, a topic hotly disputed in earlier decades, may be of little relevance to the future history of the brothers.

In his epilogue, Thompson allows his readers to ‘listen to the voices of the brothers today, and see how they envision themselves and their vocation’ in those entities that are still recruiting a significant number of lay brother vocations. This allows readers to see the very different local histories and circumstances shaping this recruitment, what lay ministries are seen as attractive in these provinces, and what formation programmes support the brethren who undertake them. Whether this will inspire other men in other provinces only time will tell, but the Order will certainly benefit from this multi-faceted study of a difficult subject.