The book proposes a new paradigm of historical practice. It questions the way we conventionally historicize the experiences of non-modern peoples, western and non-western, and makes a case for an alternative. It shows how our standard analytical devices impose modern, dualist metaphysical conditions upon all non-modern realities, thereby authorizing us to align those realities with our own modern ontological commitments, fundamentally altering their contents in the process. The net result is a practice that homogenizes the past’s many different ways of being human. To produce histories that are more ethically defensible, more philosophically robust, and more historically meaningful, we need to take an ontological turn in our practice. We need to cultivate a non-dualist historicism that will allow us to analyse each past reality on its own ontological terms, as a more or less autonomous world unto itself. The work is divided into three parts. To highlight the limitations of conventional historicist analysis and the need for an alternative, Part One (chapters 1-5) critically scrutinizes our standard modern accounts of the politeia (“way of life”) of classical Athens, the book’s primary case study. Part Two (chapters 6-9) draws on a wide range of historical, ethnographic, and theoretical literatures to frame ethical and philosophical mandates for the proposed ontological turn. To illustrate the historical benefits of this alternative paradigm, Part Three (chapters 10-16) then shows how it allows us to produce an entirely new and more meaningful account of the Athenian politeia. The book is expressly written to be accessible to a non-specialist, cross-disciplinary readership.