Brian P. Owensby's New World of Gain is a fascinating study of moral economy. Owensby's intellectual lodestar is Karl Polanyi, whose classic work, The Great Transformation (1944), describes the long nineteenth-century process by which Western societies disembedded markets from sociality and the pursuit of gain became a natural “backdrop condition” to everyday exchanges (p. 4). Owensby channels Polanyi but contends that a time line rooted in European industrial capitalism ignores earlier and global histories in which paradigms of gain and exploitation came up against people who doggedly sustained “substantive mutuality,” “that cluster of ideas, actions, and commitments anchored in gift, reciprocity, and redistribution binding societies across time” (p. 2). He details the erosion of substantive mutuality in European philosophical thought and Paraguayan colonial society and its preservation, albeit uneven, among mission Guaraní. Within an expertly crafted and theoretically sophisticated narrative, Owensby hopes “that we might see unabashed gain-seeking from the viewpoint of those who experienced it as strange and unsettling, so that the familiar and taken-for-granted might come to seem strange and unsettling once again as a matter of broad human concern” (p. 4).New World of Gain follows conventional narrative contours for the Guaraní in colonial Paraguay, covering roughly 300 years (circa 1537 to 1810), but it distinguishes itself through an innovative reading of Guaraní-language sources now available via the online database Langues Générales d'Amérique du Sud. Owensby's application of Guaraní-language materials to a long historical narrative can be “adventurous” (his word) and will certainly promote debate, but the approach breaks new ground for ethnohistorians (p. 143).Owensby skillfully and creatively mines Jesuit lexicons to interpret traditional sources and define Guaraní values as they surface in specific moments. Building on the insights of anthropologist Bartomeu Melià especially, Owensby explains that the core of Guaraní social relationships was reciprocity, which underlay the pursuit of tecó aguĭyeí, “a state of goodness, pleasure, and health in relation to others” (p. 30). The gift and countergift sustained a social philosophy of mutuality. But these practices were not straightforward, and there were negative reciprocities, such as intervillage warfare and captive taking (pp. 28–29). For their part, Spaniards also valued gifts for the sake of continued sociality, but their social value was waning in early modern Iberia, which, unlike Guaraní society, legitimized firm social and political hierarchies. So even if the conquistadores and subsequent settlers in Paraguay recognized notions of gift reciprocity and kinship by becoming the Guaraní’s tovajá (brothers-in-law) in exchange for personal servants, they viewed these practices as a means to acquire personal servants. By the beginning of the seventeenth century, many Guaraní turned to Jesuits for protections against the avarice of encomenderos and Paulista slavers; over the course of a century the Guaraní built a mission world deeply connected to regional and Atlantic markets but insulated from the worst effects of gain.By the mid-eighteenth century, Bourbon raison d’état had arrived in the Americas, manifest through an onerous 1750 relocation order for seven missions, the king's expulsion of the Jesuits, the increased secularization of mission administration, the gradual abolition of communal service, and, finally, the arrival of a homogenizing citizenship with independence. The mission world of mutual reciprocity slowly gave way to transactional exchanges. Owensby identifies many individual and communal expressions of resistance to economy, but he also takes up several individual expressions of ambivalence toward communal responsibilities or enthusiasm for individual labor for private parties. These counterexamples provide texture to the narrative but also prove Owensby's point about the kinds of choices available in societies where an economy of gain was actively applied to resistant communities: “It makes its own milieu by eroding solidarities and giving people few options beyond acquiescing to a certain kind of liberty and calling it a matter of human nature” (p. 251).The final substantive chapter intriguingly reviews how Enlightenment philosophes employed or actively ignored the example of the Guaraní-Jesuit missions. While some, like Voltaire, mocked the missions as Jesuit theocracies, others used them as idyllic foils to a Europe in the grips of avarice. The abbé de Raynal sharply critiqued European imperialism's destruction of Indigenous communities while admiring, in a markedly Rousseauian fashion, the “almost natural expression of concord” to be found in the “forests” (quoted in p. 278). The absence of the missions in Adam Smith's writings is telling because the success of the missions along purportedly primitive lines of reciprocity worked against Smith's stadial thesis that transactional exchanges were natural and humankind's ultimate productive destiny. Owensby deems this Enlightenment interest in the missions “a story Europeans were telling themselves about themselves through an imagined relationship to others, not a story that had an actual role for those others,” which puts his own anthropological narrative of Guaraní substantive mutuality in relief (p. 274).In beautiful prose, New World of Gain builds a compelling narrative of the Guaraní mission world that will interest scholars and students of the colonial Río de la Plata but equally entice a much broader audience, including Europeanists, economic historians, and proponents of the global turn. This book promises to spark debate and dialogue for many years to come.