Agential realism is a theory proposed by Karen Barad, in which the universe comprises phenomena which are "the ontological inseparability of intra-acting agencies". Intra-action, a neologism introduced by Barad, signals an important challenge to individualist metaphysics. For Barad, phenomena or objects do not precede their interaction, rather, 'objects' emerge through particular intra-actions. Thus, apparatuses, which produce phenomena, are not assemblages of humans and nonhumans (as in actor-network theory). Rather, they are the condition of possibility of 'humans' and 'non-humans', not merely as ideational concepts, but in their materiality. Apparatuses are 'material-discursive' in that they produce determinate meanings and material beings while simultaneously excluding the production of others. What it means to matter is therefore always material-discursive. Barad takes their inspiration from physicist Niels Bohr, one of the founders of quantum physics. Barad's agential realism is at once an epistemology (theory of knowing), an ontology (theory of being), and an ethics. For this, Barad employs the term onto-epistemology. Because specific practices of mattering have ethical consequences, excluding other kinds of mattering, onto-epistemological practices are always in turn onto-ethico-epistemological. Much of Barad's scholarly work has revolved around their concept of "agential realism," and their theories hold importance for many academic fields, including science studies, STS (Science, Technology, and Society), feminist technoscience, philosophy and philosophy of science, feminist theory, and, of course, physics. In addition to Bohr, their work draws a great deal on the works of Michel Foucault and Judith Butler, as demonstrated in their influential article in the feminist journal differences, "Getting Real: Technoscientific Practices and the Materialization of Reality." Barad's original training was in theoretical physics. Their book, Meeting the Universe Halfway, (2007), includes in-depth discussions of Stern–Gerlach experiments, Bell inequalities, delayed-choice quantum eraser experiments, the Kochen–Specker theorem and other topics in quantum physics from Barad's neo-Bohrian perspective. In this book, Barad also argues that 'agential realism,' is useful to the analysis of literature, social inequalities, and many other things. This claim is based on the fact that Barad's agential realism is a way of understanding the politics, ethics, and agencies of any act of observation, and indeed any kind of knowledge practice. According to Barad, the deeply connected way that everything is entangled with everything else means that any act of observation makes a "cut" between what is included and excluded from what is being considered. Nothing is inherently separate from anything else, but separations are temporarily enacted so