In Rethinking Metaphysics, Amie Thomasson aims to change how we think about metaphysics: what it can do, and why it matters. Traditional metaphysics has aimed to discover deep truths about the world. But this has led to rivalries with science, epistemological mysteries, and a despairing scepticism about how we could gain knowledge in metaphysics. Thomasson argues that the problems with prior approaches to metaphysics arise from a problematic assumption that all discourse functions in the same way. Drawing on work in linguistics, she shows how to develop a richer view of linguistic functions that enables us to see why this assumption leads us astray. By better understanding the plurality of linguistic functions, she argues, we can also disentangle ourselves from many old metaphysical problems--including problems about properties, numbers, morality and modality. In place of the traditional model, we should think of metaphysics as work in conceptual engineering--including both a reverse engineering project aimed at understanding how various parts of our language and conceptual scheme work and what functions they serve, and a constructive engineering project that investigates what concepts and language we should use and how we should use them. Rethinking metaphysics as conceptual engineering in this way enables us to avoid the problems of traditional metaphysics, while also demonstrating the perennial importance of metaphysics to human life.