This book discusses the prodigious output of one of the most influential proponents of social theory, Professor Karen Barad. Her work attracts a wide readership in feminist theory and politics, philosophy and science studies, and she pursues a particular interdisciplinary approach-"diffraction"-to pursue links and connections between these disciplines. Her new terminology, including terms like "intra-action", has been widely explored and applied. She shows how these terms have been developed from her interest in quantum theory, especially the work of Niels Boehr.This book is an "immanent critique", exploring the processes by which different academic concerns and schools have been connected and treated as examples of a very general account of how the whole universe works, which Barad terms "agential realism". There is no intention here to reject or dismiss these arguments, to replace them with a rival account, or to adopt some detached "objective" stance, although any alternatives which occur during the process are acknowledged and briefly discussed. The main objective in this book is to consider the consistency of Barad’s arguments and how they have been used in actual discussions.Some of the supporting work, by other authors like Haraway, Kirby, Schrader and Ziarek, is also considered in six chapters covering the quantum world, animals and machines as nonhuman agents, social relations as intra-actions, diffraction as a method, and general philosophical underpinnings.