In this book, Marshall Sahlins expands on his recent two-part article in the Journal of the Royal Anthropological Institute on the nature of kinship and his reply to critics. As a work of theoretical argument, it stands out in anthropology for two main reasons. First, it is an extended essay rather than a monograph, which is relatively uncommon in anthropology, but a mode of writing in which Sahlins is very comfortable. As he says, the work is an ‘among-the’ text, drawing on ethnographic examples of life ‘among the’ Korowai, Pulau Langkawi, Wari’, and so on (2). Moreover, as an essay, it is propelled by its argument. Throughout, the essayist spars with several different schools of thought. This leads to the second distinctive attribute of the work. It argues for a universal definition of kinship that draws from the universals of social experience. ‘What Kinship Is’ is humanity’s fundamentally transpersonal mode of life, or the ‘mutuality of being’ (2). ‘What Kinship Is Not’ is an expression of innate patterns of reciprocal altruism toward genealogical relatives, nor is it extensions of primary kin categories to important consociates, nor a unitary basis of social order. In this respect the book will likely provoke a major debate, not just on whether kinship is in fact the mutuality of being, but whether and how anthropology should contribute to universal questions.