According to Karen Barad's theory of agential realism, 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 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 one can examine something long enough to gain knowledge about it. This view of knowledge provides a framework for thinking about how culture and habits of thought can make some things visible and other things easier to ignore or to never see. For this reason, according to Barad, agential realism is useful for any kind of feminist analysis, even if the connection to science is not apparent.
- They define agency as a relationship and not as something that one "has."
- The scientist is always part of the apparatus, and one needs to understand that his/her/their participation is needed in order to make scientific work more accurate and more rigorous. This differs from the view that political critiques of science seek to undermine the credibility of science; instead, Barad argues that this kind of critique actually makes for better, more credible science.
- They argue that politics and ethical issues are always part of scientific work, and only are made to seem separate by specific historical circumstances that encourage people to fail to see those connections. They use the example of the ethics of developing nuclear weapons to argue this point, by claiming that the ethics and politics are part of how such weapons were developed and understood, and therefore part of science, and not merely of the "philosophy of science" or the "ethics of science." This differs from the usual view that one can strive for a politics-free, bias-less science.
- Nevertheless, they argue against moral relativism, which, according to Barad, uses science's "human" aspects as an excuse to treat all knowledge, and all ethical frameworks, as equally false. They use Michael Frayn's play Copenhagen as an example of the kind of moral relativism that they find problematic.
- They also reject the idea that science is "only" a language game or set of fictions produced only by human constructions and concepts. Although the scientist is part of the "intra-action" of the experiment, humans (and their cultural constructs) do not have complete control over everything that happens. Barad expresses this point by saying, in Getting Real, that although scientists shape knowledge about the universe, you can't ignore the way the universe "kicks back."
These points on science, agency, ethics, and knowledge reveal that Barad's work is similar to the projects of other science studies scholars such as Bruno Latour, Donna Haraway, Andrew Pickering, and Evelyn Fox Keller. Barad's notion of "phenomenon" has also been compared to analogous concepts in the work of Ian Hacking and Nancy Cartwright.
- Barad, Karen (1998). "Getting real: technoscientific practices and the materialization of reality". differences: A Journal of Feminist Cultural Studies. 10 (2): 87–128. OCLC 95847344. Abstract. Archived 2015-02-20 at the Wayback Machine
- Schaffer, Kathryn; Barreto Lemos, Gabriela (2019). "Obliterating Thingness: An Introduction to the "What" and the "So What" of Quantum Physics". Foundations of Science. doi:10.1007/s10699-019-09608-5.
Barad (who theirself was trained as a physicist) has opened up entirely new communities of interest in quantum phenomena. [...] Citing Barad, scholars in the arts, humanities, and many interdisciplinary fields now write about the “observer effect” and “entanglement”—technical physics concepts—in work that has a distinctly social or political (that is, not primarily physics-based) emphasis.
- Barad, Karen (2007). Meeting the Universe Halfway: Quantum Physics and the Entanglement of Matter and Meaning. Durham, North Carolina: Duke University Press. ISBN 9780822339175. OCLC 894219980.
- Rouse, Joseph (2004). "Barad's Agential Realism". Hypatia. 19 (1): 142–161. doi:10.1111/j.1527-2001.2004.tb01272.x. S2CID 11367786.
- Hollin, Gregory; Forsyth, Isla; Giraud, Eva; Potts, Tracey (2017). "(Dis)entangling Barad: Materialisms and ethics" (PDF). Social Studies of Science. 47 (6): 918–941. doi:10.1177/0306312717728344. PMID 28914174. S2CID 206513876.