Limpieza de sangre was the early modern Iberian conceit of ‘blood purity’ that condemned the Christian descendants of Jews and Muslims (called conversos and moriscos) as irrevocably ‘stained’ by their ancestors’ religious infidelity. Limpieza has received much scholarly attention in past decades, due not only to its undeniable poignancy as an object of cultural history but also to its ominous resonance with more familiar forms of modern bigotry. As we observe Spanish theologians, jurists and administrators across four centuries justifying and enforcing a system of hereditary hierarchy and exclusion – and doing so by way of pejoratives such as ‘impure’, ‘infected’ and ‘ugly’ – we perceive parallels with the scientific racism and anti-Semitism that helped shape some of the twentieth century's worst calamities.

Earlier studies of blood purity centred on the ideological and prescriptive content of the so-called ‘statutes of limpieza’ that proliferated in the Hispanic world after the mid-fifteenth century – these were codes excluding conversos from honourable civic and ecclesiastical communities. However, more recent research looks beyond the statutes and into the various processes and protocols they engendered, such as the widespread genealogical investigations necessary to substantiate one's purity. These studies reveal that, while the limpieza statutes were tightly theorised, in practice they tended to be applied and ignored opportunistically rather than systematically, and were rife with fraud and misrepresentation. Similarly, while intended to marginalise religious and ethnic Others, the statutes were frequently invoked against elites, as rivals denounced one another in competition for prestigious offices in the Church and the royal bureaucracy. Wielding it as a political weapon rather than a fixed set of principles, those who invoked blood purity constantly adapted its meaning to meet their rhetorical needs.

These revelations regarding the inconsistency of limpieza are especially useful with regard to the Spanish western hemisphere. Had it consisted of clear and static criteria, the notion of blood purity should have been mostly irrelevant and inert in America, as neither the region's native nor its African-descended peoples were conversos. Nonetheless, the iconic themes of limpieza survived the transatlantic voyage, reformulated and retrofitted to the unique social, religious and demographic conditions of the New World. While limpieza colonised and imposed its categories on America, it also naturalised and adapted to its new environment, eventually becoming a different creature altogether.

Considering this, El peso de la sangre, recently published by El Colegio de México, is a welcome contribution to the historiography. Acknowledging and navigating the gap between the theories and practices of social quality in the Hispanic world, it effectively illuminates the complex and twisting process by which a late medieval expression of Iberian anti-Semitism gradually evolved, by the nineteenth century, into an ideological pillar of the hierarchy of castas (people of mixed heritage) in Spanish America. Collectively, the book's contributors emphasise the discursive and procedural intersection of three discrete concepts: nobility, limpieza and mestizaje (ethnic or racial mixture). These issues are notoriously difficult to unravel because in the documents they often tangle with one another in a classic loop of circular reasoning – one is clean because he is not mestizo, which ennobles him, which proves he is clean. According to the theorists of limpieza, ‘cleanliness’ was a religious quality, ‘mestizaje’ was an ethnic process, and nobility was a fact of genealogy. Yet when early modern subjects actually invoked them, whether in self-promotion or to denounce rivals, limpieza was genealogical (de linaje limpio), mestizaje was religious (sin raza de idolatría), and nobility was an ethnic trait (as when Spaniards compared themselves favourably to Indians and Africans and their descendants). In examining these themes both individually and in concert, the book helps clarify where one ends and the next begins.

As an edited volume rather than a monograph, El peso de la sangre varies its approach methodologically, chronologically and geographically. This strategy recognises the persistent evolution of purity across time and space as well as the uneven ways that institutions on both sides of the Atlantic participated in the discourse. Max S. Hering Torres opens the volume with an overview of the social, political and theological origins of limpieza. The book continues with several chapters charting the uses (and abuses) of claims of ancestral ‘cleanliness’ and nobility in late medieval and early modern Iberia. From there, the volume broadens its focus to include America. Javier Sánchiz introduces the topic with a historiographical essay, which is followed by four empirical studies of the discourse among elite colonial institutions in Lima, Mexico City and Santa Fé (Bogotá). Together, Nikolaus Böttcher and Norma Angélica Castillo Palma confirm that colonial peoples applied Iberian notions of religious merit to their efforts to understand and police mestizaje, such that by the late eighteenth century skin colour had become a shorthand way to assess character, orthodoxy and merit. They also note the phenomenon of ‘Indian limpieza’, a parallel rhetoric by which native nobles distinguished themselves from commoners and mestizos. Finally, Guillermo Zermeño's epilogue traces the ultimate abolition of limpieza and the posthumous redemption of the castas in revolutionary Mexico, symbolised by the ‘mestizophilic’ Fiesta de la Raza of 1917. Seeking a new nationalism, Mexican liberals and revolutionaries rescued mestizaje from its long association with bad character, illegitimacy and impurity, and declared it the authentic essence of a modern, progressive nation.

El peso de la sangre will appeal to a broad audience. While largely confirming rather than challenging other recent studies of limpieza and the casta system, it helpfully clarifies the historical and ideological links between them. As such, it will be highly useful as an introduction to the religious and socio-political origins of limpieza as well as an empirical look at its true place in the everyday strategies of early modern subjects. Going further, by revealing the ideological and procedural influences of limpieza on early modern discourses about mestizaje and nobility, El peso de la sangre is also a prehistory of the meaning of race in Spanish America. In this way it broadens our understanding of one the most important and complex issues in Latin American studies.