New World of Gain tells the story of a collision, that of “people and their ideas about what is worth doing in the world and why” (p. 16). Brian P. Owensby examines a foundational confrontation in the Río de la Plata basin between Europeans and the Guaraní people, spanning from the early sixteenth century to the turn of the nineteenth century. At the heart of this collision lay two profoundly different ways of organizing economic and social life. On one side stood the Guaraní system of “substantive mutuality”—grounded in gift-giving and reciprocity—which aimed to ensure that all members of society honored their obligations to one another. On the other side stood Spaniards driven by gain—“the desire and capacity to benefit materially at the expense of others, without concern for reciprocity” (p. 3). This was not merely an encounter between different societies but a clash over the terms of human sociability. At stake was whether people should live in aguĭyeí (goodness, health, and right relations with others through reciprocity) (p. 30) or accept a world where every person could become prey to another.

The book examines what happened when people without experience of individual gain-seeking as an organizing force confronted men who aimed to benefit at others’ expense. Owensby begins by establishing baselines for both Guaraní and Spanish social understandings prior to contact (chapter 1). He illustrates how substantive mutuality structured Guaraní societies through concrete practices of gift-giving and reciprocity, with ritual cannibalism serving as a dramatic expression of this system. Intriguingly, he identifies overlapping concepts in European theological understandings of love, suggesting that while the two worldviews were different, they were not entirely incompatible.

Yet such theological ideals were not systematically shared across Spanish society, and certainly not among Spanish settlers in the Americas. The initial encounter centered on material exchanges that revealed fundamentally different understandings of obligation and exploitation (chapter 2). Spanish settlers brought instrumental and exploitative impulses regarding Indigenous labor and women, while the Guaraní attempted to interpret these interactions through their own frameworks. As settler violence intensified, Habsburg authorities attempted to mobilize royal justice to protect Indigenous peoples (chapter 3). Spanish law stipulated that the king bound all vassals together in a shared social order founded on love and royal justice. Yet in practice, imperial legal order in the Americas proved malleable, bent at the local level to serve the interests of exploitative colonists.

By the early seventeenth century, the Guaraní sought alliance with Jesuit missionaries as a means of escaping settlers’ unrelenting exploitation (chapter 4). The result was the mission world, a network of settlements administered by the Jesuits, which Owensby presents not as a simple European imposition but as the outcome of a pact among the Guaraní, the Habsburg kingdom, and the Jesuits. This tripartite agreement rested on finding overlapping practices between contending worldviews, enabling cohabitation within well-defined polities. Crucially, this cohabitation enabled not just survival of Guaraní substantive mutuality but shared economic prosperity (chapter 5).

A central theme in Owensby’s analysis is that cohabitation rested more often on misunderstandings, mistranslations, and unintended overlaps than on systematic mutual comprehension; groups who did not always understand each other nonetheless found ways to accommodate one another’s practices while generating prosperity. This prosperity was real yet fragile, at once local and globally linked. The mission world suffered from international diplomacy that redrafted imperial control in the region. It ultimately collapsed when Bourbon kings came to power in Spain, eliminating the legal protections that had sustained the mission pact (chapter 6). Gain logic, no longer confined to settlers, was now advocated by broader segments of European societies. The new regime encouraged a gain-centered political economy, less tolerant of the ambiguities and accommodations that had sustained the mission world (chapter 7).

Owensby engages deeply with sources that enable him to place Europeans and Guaraní on more equal terms. Drawing on archival materials, anthropological scholarship, and bilingual dictionaries of both Guaraní and Spanish, he demonstrates how historians have at times mistranslated sources, particularly Guaraní documents. Most significantly, he shows how historical actors themselves frequently misunderstood one another, building relationships upon these misunderstandings, which nonetheless enabled different worldviews to coexist and generate economic prosperity. Owensby carefully situates each source within its own context and provides multiple readings, recognizing how historical actors themselves made different readings of the same events and texts. New World of Gain thus makes contributions to colonial history through the granularity with which it describes processes of contact and resistance, and more fundamentally, through its analysis of competing understandings of how to organize social and economic life. In dialogue with recent research on Indigenous economic history, future scholarship might explore what followed and occurred alongside the disintegration of Guaraní collective structures: whether individual Guaraní successfully navigated new monetary relationships, or whether other institutional barriers systematically excluded them from this gain-centered system. Regardless, Owensby offers business historians interesting insights: his work illuminates how prosperity could emerge from paths other than a single evolutionary trajectory, and how different peoples understood what humans owe one another.

Yet New World of Gain does more than revisit the well-known history of Jesuit missions in Paraguay. Owensby effectively situates his story within a broader narrative about the origins of contemporary economic systems. Drawing on Karl Polanyi’s insight that gain became “a mainspring of action,” achieving its apotheosis with industrial market capitalism (p. 2), Owensby critiques Polanyi’s Eurocentric chronology, arguing that the history of gain extends much earlier—at least to Europe’s expansion beyond the Old World. What was unfolding in the Río de la Plata basin demonstrated to European political economists that prosperity could emerge from a social order built upon mutuality rather than gain alone (chapter 8). Owensby thus positions the Guaraní’s persistent practice of substantive mutualism as a countermovement against the encroachment of gain logic, not just in South America but as part of a struggle for the whole world to witness. The richness of this framing also brings into focus certain conceptual questions, particularly since scholars have challenged Polanyi’s equation of gain with capitalism’s foundations—a link Owensby appears to adopt. The concept of “gain” invites somewhat further theoretical development in his account, evolving from simple self-interest to a foundational element of capitalist social relationships without clearly delineated boundaries.

These ambiguities notwithstanding, Owensby has produced a compelling and richly detailed narrative. The book should interest historians concerned with global economic history, scholars of colonial Latin America, and anyone examining how economic systems structure human relationships. His meticulous attention to sources, excavating layers of meaning and misunderstanding, denaturalizes familiar assumptions about economic behavior and challenges assumptions about the inevitable pathways through which prosperity may emerge.