Matéria e sentido (Barad 2007)

Matéria e sentido (Barad 2007)

BARAD, Karen. 2007. Meeting the universe halfway: quantum physics and the entanglement of matter and meaning. Durham: Duke University Press.


It is important to go slowly and carefully. (Barad 2007:81)

NÃO É POSSÍVEL SEPARAR MATÉRIA E SENTIDO (eles são inextricavelmente ligados)

Matter and meaning are not separate elements. They are inextricably fused together (Barad 2007:3)

Even atoms, whose very name, atomos (atomos), means “indivisible” or “uncuttable,” can be broken apart. But matter and meaning cannot be dissociated, not by chemical processing, or centrifuge, or nuclear blast. (Barad 2007:3)


[C]ontemporary physics makes the inescapable entanglement of matters of being, knowing, and doing, of ontology, epistemology, and ethics, of fact and value, so tangible, so poignant. (Barad 2007:3)

“Does one as a physicist have the moral right to work on the practical exploitation of atomic energy?” Heisenberg’s haunting question to Bohr hangs in the air throughout Copenhagen. (Barad 2007:7)


Let’s look more closely at what Heisenberg’s uncertainty principle says. Heisenberg does not say that we can’t have any knowledge about a particle’s position and momentum; rather, he specifies a trade-off concerning how well we can know both quantities at once: the more we know about a particle’s position, the less we know about its momentum, and vice versa. (Barad 2007:7)

The fact remains that the common public conception of the uncertainty principle is (at best) the epistemic version that Heisenberg himself retracted. But even more unfortu- nate, surely, is the fact that many physics textbooks, physics students, and professional physicists share this misconception. (Barad 2007:118)

INTERPRETAÇÃO DE COPENHAGEN (complementaridade-Bohr e incerteza-Heisenberg)

Bohr and Heisenberg were two of the great leaders of the quantum revolution in physics. Their respective interpretations of quantum physics—complementarity and uncertainty—constitute the nucleus of the so-called Copenhagen interpretation of quantum mechanics. (Barad 2007:3)


[Q]uantum theory leads us out of the morass that takes absolutism and relativism to be the only two possibilities. (Barad 2007:18)

Quantum physics undercuts reductionism as a worldview or universal explanatory framework. (Barad 2007:24)

Quantum leaps in any case are unavoidable. (Barad 2007:38)

The epistemological and ontological issues are not circumscribed by the size of Planck’s constant. (Barad 2007:69)

In a sense, to accomplish my task, I need to “rescue” quantum theory from the problematic discourses of both its overzealous advocates and its unreflective practitioners. […] It is not my intention to contribute to the romanticizing or mysticizing of quantum theory. On the contrary, as a physicist, I am interested in engaging in a rigorous dialogue about particular aspects of specific discourses on quantum physics and their implications. (Barad 2007:67-8)

According to quantum electrodynamics, the “vacuum” (which, classically speaking, refers to the void) is a state in which everything that can possibly exist exists in some potential form. The lively potentiality of the vacuum creates “vacuum fluctuations,” which produce the Lamb shift in the hydrogen spectrum. That Lamb and Retheford were able to measure this tiny shift is remarkable; that there is a possibility of measuring the effects of unrealized possibilities is nothing short of astonishing. Indeed, the Lamb shift constitutes one of the most accurate tests we have of the theory of quantum electrodynamics. (Barad 2007:92)

quantum theory exposes an essential failure of representationalism (Barad 2007:124)

A REVOLUÇÃO DE BOHR (filosofísica, política, ética e mediação técnica, para além dos binarismos) – A Bohrian ontology: phenomena and intra-actions (Barad 2007:125)

Bohr’s ideas reveals that the very notion of causality must be reconsidered, since the traditional conception—which presents only the binary options of free will and determinism—is flawed. But if causality is reworked, then power needs to be rethought. (Power relations cannot be understood as either determining or absent of constraints within a corral that merely limits the free choices of individuals.) Agency needs to be rethought. Ethics needs to be rethought. Science needs to be rethought. Indeed, taking Bohr’s interpretation seriously calls for a reworking of the very terms of the question about the relationship between science and ethics. Even beyond that, it undermines the metaphysics of individualism and calls for a rethinking of the very nature of knowledge and being. It may not be too much of an exaggeration to say that every aspect of how we understand the world, including ourselves, is changed. (Barad 2007:23)

In this book I offer a rigorous examination and elaboration of the implications of Bohr’s philosophy-physics (physics and philosophy were one practice for him, not two). (Barad 2007:24)

Bohr’s philosophy-physics is a particularly apt starting point for thinking the natural and social worlds together and gaining some important clues about how to theorize the nature of the relationship between them, since his investigations of quantum physics open up questions not only about the nature of nature but also about the nature of scientific and other social practices. In particular, Bohr’s naturalist commitment to understanding both the nature of nature and the nature of science according to what our best scientific theories tell us led him to what he took to be the heart of the lesson of quantum physics: we are a part of that nature that we seek to understand. Bohr argues that scientific practices must therefore be understood as interactions among component parts of nature and that our ability to understand the world hinges on our taking account of the fact that our knowledge-making practices are social-material enactments that contribute to, and are a part of, the phenomena we describe. (Barad 2007:26)

Bohr’s position that neither the subjects nor the objects of knowledge practices can be taken for granted, and that one must inquire into the material specificities of the apparatuses that help constitute objects and subjects. (Barad 2007:27)

Bohr’s epistemological framework, based on empirical findings in the atomic domain in the early twentieth century, offers a new understanding of fundamental philosophical issues such as the relationship between knower and known, the role of measurement, questions of meaning making and concept use, the conditions for the possibility of objective description, correct identification of the objective referent for measured properties, the nature of causality, and the nature of reality. (Barad 2007:31)

Bohr understands these issues—concerning word and world—to be inextricably linked. According to Bohr, our ability to understand the physical world hinges on our recognizing that our knowledge-making practices, including the use and testing of scientific concepts, are material enactments that contribute to, and are a part of, the phenomena we describe. (Barad 2007:32)

Bohr’s naturalist commitment to understanding both the nature of nature and the nature of science according to what our best scientific theories tell us led him to what he took to be the heart of the lesson of quantum physics: we are a part of that nature that we seek to understand. (Barad 2007:67)

Bohr’s view that philosophy is integral to physics (Barad 2007:68)

[T]he nature of the observed phenomenon changes with corresponding changes in the apparatus. (Barad 2007:106)

Bohr called into question two fundamental assumptions that support the notion of measurement transparency in Newtonian physics: (1) that the world is composed of individual objects with individually determinate boundaries and properties whose well-defined values can be represented by abstract universal concepts that have determinate meanings independent of the specifics of the experimental practice; and (2) that measurements involve continuous determinable interactions such that the values of the properties obtained can be properly assigned to the premeasurement properties of objects as separate from the agencies of observation. In other words, the assumptions entail a belief in representationalism (the independently determinate existence of words and things), the metaphysics of individualism (that the world is composed of individual entities with individually determinate boundaries and properties), and the intrinsic separability of knower and known (that measurements reveal the preexisting values of the properties of independently existing objects as separate from the measuring agencies). (Barad 2007:107)

According to Bohr, at the beginning of the twentieth century a crucial empirical fact was discovered that disproves the classical assumption that measurement interactions are continuous. This “essential discontinuity” — or “quantum jump” — characterizes quantum physics. Despite its common colloquial usage to mark a large (discontinuous) change, a quantum jump is not large at all — in fact, the term “quantum” means the smallest quantity or discrete amount that exits. In fact, this essential discontinuity is otherwise known in physics as Planck’s constant (after its founder), symbolized by h, and it is indeed an extremely small quantity. This idea of an essential discreteness or discontinuous nature was initially introduced by Max Planck in 1900 in his attempt to account for some data on blackbody radiation, which would not yield to classical physics analysis. In particular, he proposed that energy is “quantized” and exchanged in discrete amounts. The fact that h =/= 0 (i.e., that the value of Planck’s constant is not zero) marks the existence of a fundamental discontinuity of nature. The failure of Newtonian physics to take appropriate account of this discontinuity portends its downfall. (Barad 2007:108)

Bohr’s argument for the indeterminable nature of measurement interactions is based on his insight that concepts are defined by the circumstances required for their measurement. That is, theoretical concepts are not ideational in character; they are specific physical arrangements. For Bohr, measurement and description (the physical and the conceptual) entail each other (not in the weak sense of operationalism but in the sense of their mutual epistemological implication). Bohr argues that because concepts, like “position” and “momentum,” for example, are specifically embodied, mutually exclusive experimental arrangements need to be employed simultaneously (which is by definition impossible) to determine all the required features of the measurement interaction. (Barad 2007:109)

No one would suggest that because atoms are too small to see with the naked eye, we are therefore entitled to deny their existence and their relevance to our everyday lives (although we do at times successfully ignore their existence). The entity in question may be small, but its consequences may be quite profound. This is indeed true of the existence of the fundamental discontinuity. […] To the best of our knowledge, h is a universal constant. […] And this is the point. Bohr’s analysis does not depend on the size of h, only the fact that it is nonzero. […] The fact that h (Planck’s constant) is small relative to the mass of large objects does not mean that Bohr’s insights apply only to microscopic objects. It does mean that the effects of the essential discontinuity may be less evident for relatively large objects, but they are not zero. To put it another way, no evidence exists to support the belief that the physical world is divided into two separate domains, each with its own set of physical laws: a microscopic domain governed by the laws of quantum physics, and a macroscopic domain governed by the laws of Newtonian physics. Indeed, quantum mechanics is the most successful and accurate theory in the history of physics, accounting for phenomena over a range of twenty-five orders of magnitude, from the smallest particles of matter to large-scale objects. Quantum physics does not merely supplement Newtonian physics — it supersedes it. The key point is this: Bohr’s analysis of the nature of measurement interactions and the epistemological implications of his analysis are completely general (as far as we know). (Barad 2007:110)

Since observations involve an indeterminable discontinuous interaction, as a matter of principle, there is no unambiguous way to differentiate between the “object” and the “agencies of observation.” No inherent/Cartesian subject-object distinction exists. […] The boundary between the “object of observation” and the “agencies of observation” is indeterminate in the absence of a specific physical arrangement of the apparatus. What constitutes the object of observation and what constitutes the agencies of observation are determinable only on the condition that the measurement apparatus is specified. The apparatus enacts a cut delineating the object from the agencies of observation. Clearly, then, as we have noted, observations do not refer to properties of observation-independent objects (since they don’t preexist as such). (Barad 2007:114)

Abraham Pais […] wrote that “Einstein once remarked of Bohr, ‘He utters his opinions like one perpetually groping and never like one who believes to be in possession of definite truth'” (Barad 2007:121)

As I noted from the outset, my aim is not so much to provide a faithful representation of Bohr’s philosophy-physics as to propose a consistent framework for thinking about important epistemological and ontological issues. In addressing these issues, it would be just as dishonest to attribute the full development of this framework to Bohr as it would be to deny that my thinking about Bohr’s philosophy-physics is everywhere present in my formulation. (Barad 2007:123)

Bohr’s commitment to finding a way to hang on to objectivity in the face of the significant role of “subjective elements” such as human concepts in the production of phenomena underlines his opposition to idealism and relativism. Apparatuses are not Kantian conceptual frameworks; they are physical arrangements. And phenomena do not refer merely to perception of the human mind; rather, phenomena are real physical entities or beings (though not fixed and separately delineated things). Hence I conclude that Bohr’s framework is consistent with a particular notion of realism, which is not parasitic on subject-object, culture-nature, and word-world distinctions. (Barad 2007:129)

As Bohr points out, the inseparability of the object from the apparatus ‘‘entails . . . the necessity of a final renunciation of the classical ideal of causality and a radical revision of our attitude towards the problem of physical reality’’ (Bohr 1963b [1949 essay], 59–60). (Barad 2007:129)

For Bohr, things do not have inherently determinate boundaries or properties, and words do not have inherently determinate meanings. Bohr also calls into question the related Cartesian belief in the inherent distinction between subject and object, and knower and known. Indeed, Bohr’s philosophy-physics poses a radical challenge not only to Newtonian physics but also to Cartesian epistemology and its representationalist triadic structure of words, knowers, and things. (Barad 2007:138)

It might be said that the epistemological framework that Bohr develops rejects both the transparency of language and the transparency of measurement; however, even more fundamentally, it rejects the presupposition that language and measurement perform mediating functions. (Barad 2007:138)


I propose “agential realism” as an epistemological-ontological-ethical framework that provides an understanding of the role of human and nonhuman, material and discursive, and natural and cultural factors in scientific and other social-material practices, thereby moving such considerations beyond the well-worn debates that pit constructivism against realism, agency against structure, and idealism against materialism. (Barad 2007:26)

Chapter 4 is the core chapter of the book. Here I develop my central theoretical framework—agential realism. Agential realism is an epistemological, ontological, and ethical framework that makes explicit the integral nature of these concerns. This framework provides a posthumanist performative account of technoscientific and other naturalcultural practices. (Barad 2007:32)

[A]gential realism clarifies the nature of the causal relationship between discursive practices and material phenomena. (Barad 2007:34)

[A]gential realism’s reconceptualization of the nature of matter and discursive practices provides a means for taking account of the productive nature of natural as well as cultural forces in the differential materialization of nonhuman as well as human bodies. It thereby avoids the privileging of discursive over material concerns and the reinscription of the nature-culture dualism (Barad 2007:34-5)

Importantly, agential realism rejects the notion of a correspondence relation between words and things and offers in its stead a causal explanation of how discursive practices are related to material phenomena. It does so by shifting the focus from the nature of representations (scientific and other) to the nature of discursive practices (including technoscientific ones), leaving in its wake the entire irrelevant debate between traditional forms of realism and social constructivism. Crucial to this theoretical framework is a strong commitment to accounting for the material nature of practices and how they come to matter. (Barad 2007:44-5)

[A]ccording to agential realism, the analysis of entangled practices requires a nonadditive approach that is attentive to the intra-action of multiple apparatuses of bodily production. (Barad 2007:94)

There is an important sense in which the only thing that doesn’t seem to matter anymore is matter. (Barad 2007:132)

Crucially, an agential realist elaboration of performativity allows matter its due as an active participant in the world’s becoming, in its ongoing intra-activity. And furthermore it provides an understanding of how discursive practices matter. (Barad 2007:136)

[M]atter is substance in its intra-active becoming — not a thing but a doing, a congealing of agency. Matter is a stabilizing and destabilizing process of iterative intraactivity. Phenomena — the smallest material units (relational “atoms”)— come to matter through this process of ongoing intra-activity. […] [M]atter is a dynamic intra-active becoming that is implicated and enfolded in its iterative becoming. Matter(ing) is a dynamic articulation/configuration of the world. (Barad 2007:151)

In an agential realist account, apparatuses are […] dynamic (re)configurings of the world through which bodies are intra-actively materialized. (Barad 2007:169-70)


Mirrors reflect. To mirror something is to provide an accurate image or representation that faithfully copies that which is being mirrored. Hence mirrors are an often-used metaphor for representationalism and related questions of reflexivity. (Barad 2007:86)


I use the terms “diffraction” and “interference” interchangeably. That is, I side with the physicist Richard Feynman and others who drop this distinction on the basis that what is at issue in both cases is the physics of the superposition of waves. (Barad 2007:28-9)

I use the terms “diffraction” and “interference” interchangeably without granting significance to the historical contingencies by which they have been assigned different names. (Barad 2007:81)

[I]f the goal is to think the social and the natural together, to take account of how both factors matter (not simply to recognize that they both do matter), then we need a method for theorizing the relationship between “the natural” and “the social” together without defining one against the other or holding either nature or culture as the fixed referent for understanding the other. What is needed is a diffraction apparatus to study these entanglements. One way to begin to build the needed apparatus is to use the following approach: to rethink the nature of nature based on our best scientific theories, while rethinking the nature of scientific practices in terms of our best understanding of the nature of nature and our best social theories, while rethinking our best social theories in terms of our best understanding of the nature of nature and the nature of scientific theories. A diffractive methodology provides a way of attending to entanglements in reading important insights and approaches through one another. (Barad 2007:30)

[T]his book works as a diffraction grating, illuminating important material differences, relationalities, and entanglements in the lively dance of mattering, and it may be difficult to appreciate the intricacies of the pattern that is produced if significant segments of the book are skipped over. (Barad 2007:37)

As Donna Haraway suggests, diffraction can serve as a useful counterpoint to reflection: both are optical phenomena, but whereas the metaphor of reflection reflects the themes of mirroring and sameness, diffraction is marked by patterns of difference. (Barad 2007:71)

Haraway’s point is that the methodology of reflexivity mirrors the geometrical optics of reflection, and that for all of the recent emphasis on reflexivity as a critical method of self-positioning it remains caught up in geometries of sameness; by contrast, diffractions are attuned to differences—differences that our knowledge-making practices make and the effects they have on the world. (Barad 2007:72)

I will argue that there is a deep sense in which we can understand diffraction patterns — as patterns of difference that make a difference — to be the fundamental constituents that make up the world. (Barad 2007:72)

diffraction is a quantum phenomenon that makes the downfall of classical metaphysics explicit. (Barad 2007:72)

So at times diffraction phenomena will be an object of investigation and at other times it will serve as an apparatus of investigation; it cannot serve both purposes simultaneously since they are mutually exclusive; nonetheless, as our understanding of the phenomenon is refined we can enfold these insights into further refinements and tunings of our instruments to sharpen our investigations and so on. (Barad 2007:73)

To summarize, what I am interested in doing is building diffraction apparatuses in order to study the entangled effects differences make. (Barad 2007:73)

Simply stated, diffraction has to do with the way waves combine when they overlap and the apparent bending and spreading of waves that occurs when waves encounter an obstruction. Diffraction can occur with any kind of wave: for example, water waves, sound waves, and light waves all exhibit diffraction under the right conditions. (Barad 2007:74)

Surfers know this phenomenon well, since they are sometimes able to catch really nice waves on the other side of a large boulder sitting offshore. That is, they can take advantage of the diffraction patterns created by rocks or pieces of land that stick out near the shore. These surfers are literally riding the diffraction pattern. (Barad 2007:80)

It has now become routine to use diffraction experiments to determine different features of matter. Generally this works in one of two complementary ways: sometimes the goal of a diffraction experiment is to learn about the nature of the substance that is being passed through a diffraction grating, and sometimes it’s to learn about the diffraction grating itself. (Barad 2007:83)

While reflection has been used as a methodological tool by scholars relying on representationalism, there are good reasons to think that diffraction may serve as a productive model for thinking about nonrepresentationalist methodological approaches. (Barad 2007:88)

important aspects of diffraction that make it a particularly effective tool for thinking about socialnatural practices in a peformative rather than representationalist mode (Barad 2007:88)

First and foremost, as Haraway suggests, a diffractive methodology is a critical practice for making a difference in the world. It is a commitment to understanding which differences matter, how they matter, and for whom. It is a critical practice of engagement, not a distance-learning practice of reflecting from afar. The agential realist approach that I offer eschews representationalism and advances a performative understanding of technoscientific and other naturalcultural practices, including different kinds of knowledge-making practices. According to agential realism, knowing, thinking, measuring, theorizing, and observing are material practices of intra-acting within and as part of the world. What do we learn by engaging in such practices? We do not uncover preexisting facts about independently existing things as they exist frozen in time like little statues positioned in the world. Rather, we learn about phenomena — about specific material configurations of the world’s becoming. The point is […] to understand and take account of the fact that we too are part of the world’s differential becoming. And furthermore, the point is […] that practices of knowing are specific material engagements that participate in (re)configuring the world. Which practices we enact matter — in both senses of the word. Making knowledge is not simply about making facts but about making worlds, or rather, it is about making specific worldly configurations (Barad 2007:90-1)

The physical phenomenon of diffraction makes manifest the extraordinary liveliness of the world. (Barad 2007:91)

diffraction gratings can be used to exhibit some of the smallest details of nature (at least the smallest levels that we have successfully explored). For example, diffraction gratings can be used to measure the spectrum of light that is characteristic of each kind of atom. Each atom in the periodic table has a characteristic set of energy states (different “orbits” that the electron can be in), and when an electron “jumps” from a higher energy level to a lower one, it emits light of a corresponding wavelength (e.g., the visible spectrum of hydrogen has a red line, a blue line, and two violet lines). Therefore the light spectrum of an atom indicates its possible energy levels. The differences in energy levels are tiny (we’re talking about changes inside an atom). (Barad 2007:91-2)

When it comes to the “interface” between a coffee mug and a hand, it is not that there are x number of atoms that belong to a hand and y number of atoms that belong to the coffee mug. Furthermore, […] it a well-recognized fact of physical optics that if one looks closely at an “edge,” what one sees is not a sharp boundary between light and dark but rather a series of light and dark bands — that is, a diffraction pattern. (Barad 2007:156)

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the primary ontological unit is not independent objects with independently determinate boundaries and properties but rather what Bohr terms “phenomena.” In my agential realist elaboration, phenomena do not merely mark the epistemological inseparability of observer and observed, or the results of measurements; rather, phenomena are the ontological inseparability of agentially intra-acting components. […] Significantly, phenomena are not mere laboratory creations but basic units of reality. The shift from a metaphysics of things to phenomena makes an enormous difference in understanding the nature of science and ontological, epistemological, and ethical issues more generally. (Barad 2007:33)

Phenomena, according to my agential realist account, are neither individual entities nor mental impressions, but entangled material agencies […]. The agential realist understanding that I propose is a non- representationalist form of realism that is based on an ontology that does not take for granted the existence of “words” and “things” and an epistemology that does not subscribe to a notion of truth based on their correct correspondence. Agential realism offers the following elaboration of Hacking’s critique of representationalism: experimenting and theorizing are dynamic practices that play a constitutive role in the production of objects and subjects and matter and meaning. As I will explain, theorizing and experimenting are not about intervening (from outside) but about intra-acting from within, and as part of, the phenomena produced. (Barad 2007:56)

Since there is no inherent distinction between object and instrument, the property measured cannot meaningfully be attributed to either an abstract object or an abstract measuring instrument. That is, the measured value is neither attributable to an observation-independent object, nor is it a property created by the act of measurement […]. My reading is that the measured properties refer to phenomena, remembering that the crucial identifying feature of phenomena is that they include “all relevant features of the experimental arrangement.” […] This shift in referentiality is a condition for the possibility of objective knowledge. That is, a condition for objective knowledge is that the referent is a phenomenon (and not an observation-independent object). (Barad 2007:56)

Since individually determinate entities do not exist, measurements do not entail an interaction between separate entities; rather, determinate entities emerge from their intra-action. I introduce the term “intra-action” in recognition of their ontological inseparability, in contrast to the usual “interaction,” which relies on a metaphysics of individualism (in particular, the prior existence of separately determinate entities). A phenomenon is a specific intra-action of an “object” and the “measuring agencies”; the object and the measuring agencies emerge from, rather than precede, the intra-action that produces them. Crucially, then, we should understand phenomena not as objects-in-themselves, or as perceived objects (in the Kantian or phenomenological sense), but as specific intra-actions. Because the basis of this ontology is a fundamental inseparability, it cuts across any Kantian noumena-phenomena distinction: there are no determinately bounded or propertied entities existing “behind” or as the causes of phenomena. Not only is this ontological understanding of phenomena consistent with Bohr’s insights; it is also consistent with recent experimental and theoretical developments in quantum physics (see chapter 7). (Barad 2007:128)

[P]henomena do not merely mark the epistemological inseparability of observer and observed, or the results of measurements; rather, phenomena are the ontological inseparability/entanglement of intra- acting “agencies.” That is, phenomena are ontologically primitive relations — relations without preexisting relata. The notion of intra-action (in contrast to the usual “interaction,” which presumes the prior existence of independent entities or relata) represents a profound conceptual shift. It is through specific agential intra-actions that the boundaries and properties of the components of phenomena become determinate and that particular concepts (that is, particular material articulations of the world) become meaningful. Intra-actions include the larger material arrangement (i.e., set of material practices) that effects an agential cut between “subject” and “object” (in contrast to the more familiar Cartesian cut which takes this distinction for granted). That is, the agential cut enacts a resolution within the phenomenon of the inherent ontological (and semantic) indeterminacy. In other words, relata do not preexist relations; rather, relata-within-phenomena emerge through specific intra-actions. Crucially, then, intra-actions enact agential separability — the condition of exteriority-within-phenomena. The notion of agential separability is of fundamental importance, for in the absence of a classical ontological condition of exteriority between observer and observed, it provides an alternative ontological condition for the possibility of objectivity. Moreover, the agential cut enacts a causal structure among components of a phenomenon in the marking of the “measuring agencies” (“effect”) by the “measured object” (“cause”). It is in this sense that the measurement can be said to express particular facts about that which is measured; that is, the measurement is a causal intra-action and not “any old playing around.” Hence the notion of intra-action constitutes a reworking of the traditional notion of causality. (Barad 2007:139-40)

[P]henomena are not the mere result of laboratory exercises engineered by human subjects; rather, phenomena are differential patterns of mattering (“diffraction patterns”) produced through complex agential intra-actions of multiple material-discursive practices or apparatuses of bodily production, where apparatuses are not mere observing instruments but boundary-drawing practices— specific material (re)configurings of the world — which come to matter. (Barad 2007:140)

Reality is composed not of things- in-themselves or things-behind-phenomena but of things-in-phenomena. (Barad 2007:140)

It is important to keep in mind that Bohr is making a point about the inherent ambiguity of bodily boundaries and the resolution of those boundaries through particular complementary cuts/practices. He is not making a point about the nature of conscious subjective experience, that is, about phenomena in the phenomenologist’s sense. (Barad 2007:155)

The boundaries and properties of an “object” are determinate only within and as part of a particular phenomenon. Therefore, by the logic of Bohr’s own analysis, the boundaries and properties of an apparatus are not well defined outside its determination within a larger phenomenon. (Barad 2007:160)

Bohr insists that an “unambiguous [i.e., objective] account of proper quantum phenomena must, in principle, include a description of all relevant features of the experimental arrangement” (Bohr 1963c [1958 essay], 4). Now, to determine all its relevant features, it is necessary to characterize the entire experimental apparatus (or at least all the features that are relevant) by involving it within a larger phenomenon. That is, the apparatus that is to be characterized (i.e., measured) must be the “object of observation” within some larger phenomenon involving its intra-action with an auxiliary apparatus. This is necessary so that the “object apparatus” within the larger phenomenon effects its marks on another “part” of the larger phenomenon (which includes the auxiliary apparatus). In other words, to measure its characteristics (as part of a larger phenomenon), the original apparatus in question would have to become the “object” of investigation in its intra-action with an auxiliary apparatus, thereby involving it in some larger phenomenon. Since it is not possible for the apparatus to simultaneously be both measured object and measuring instrument, the apparatus cannot be fully characterized and function according to its (“original”) purpose simultaneously. Or to put it another way, any attempt to measure the “original” apparatus’s characteristics will require its involvement within a larger phenomenon whereby it is positioned as the object of investigation, thereby excluding its role as an agency of observation. The measurement of the apparatus entails a different phenomenon from the original one, and the connection of the two different phenomena would require a third, yet larger phenomenon entailing these. Hence the “outside” boundary, like the “inside” boundary, is not determinate in the absence of its involvement in a larger phenomenon. In other words, there are no intrinsic boundaries, and even what is “inside” and what is “outside” are intrinsically indeterminate. The logic of Bohr’s own argument undercuts the conception of the apparatus as a static and bounded laboratory setup and the human as the set designer, interpreter, and spokesperson for the performance of nature. (Barad 2007:160-1)

INTRA-AÇÃO (animismo?)

The neologism “intra-action” signifies the mutual constitution of entangled agencies. That is, in contrast to the usual “interaction,” which assumes that there are separate individual agencies that precede their interaction, the notion of intra-action recognizes that distinct agencies do not precede, but rather emerge through, their intra-action. It is important to note that the “distinct” agencies are only distinct in a relational, not an absolute, sense, that is, agencies are only distinct in relation to their mutual entanglement; they don’t exist as individual elements. […] Crucially, […] the notion of intra-action constitutes a radical reworking of the traditional notion of causality. […] A lively new ontology emerges: the world’s radical aliveness comes to light in an entirely nontraditional way that reworks the nature of both relationality and aliveness (vitality, dynamism, agency). (Barad 2007:33)


Butler’s conception of materiality is limited by its exclusive focus on human bodies and social factors, which works against her efforts to understand the relationship between materiality and discursivity in their indissociability. (Barad 2007:34)


During the past decade, technological progress in experimental physics has opened up an entirely new empirical domain: the world of “experimental metaphysics.” That is, questions previously thought to be a matter solely for philosophical debate have been brought into the orbit of empirical inquiry. This is a striking development because it allows scientists to explore metaphysical issues in the laboratory (Barad 2007:35)


[M]y project […] does not merely offer insights about the nature of scientific practices but also makes a constructive contribution to the field of science being studied. That is, my project is not merely a reflection on science but takes these insights about scientific practices and about nature (the two key ingredients in Bohr’s interpretation) and diffracts them back onto the science itself, thereby making a specific scientific contribution to an active scientific research field (i.e., the foundations of quantum physics). In particular, I argue that the conceptual shifts derived from my diffractive methodology not only reconfigure our understanding of the nature of scientific and other material-discursive practices but also are significant and robust enough to actually form the basis for a new interpretation of quantum physics. (Barad 2007:36)

I argue that agential realism can in fact be understood as a legitimate interpretation of quantum mechanics, addressing crucial issues that Bohr’s framework of complementarity does not satisfactorily resolve.(Barad 2007:94)


ethical concerns are not simply supplemental to the practice of science but an integral part of it. But more than this, […] values are integral to the nature of knowing and being. Objectivity is simultaneously an epistemological, ontological, and axiological issue, and questions of responsibility and accountability lie at the core of scientific practice. The correct identification of the objective referent of scientific practices of theorizing and experimenting requires an accounting of the ethical (as well as epistemological and ontological) concerns. It is not possible to extricate oneself from ethical concerns and correctly discern what science tells us about the world. Realism, then, is not about representations of an independent reality but about the real consequences, interventions, creative possibilities, and responsibilities of intra-acting within and as part of the world. (Barad 2007:37)

How different ethics looks from the vantage point of constitutive entanglements. What would it mean to acknowledge that the “able-bodied” depend on the “disabled” for their very existence? What would it mean to take on that responsibility? What would it mean to deny one’s responsibility to the other once there is a recognition that one’s very embodiment is integrally entangled with the other? (Barad 2007:158)


Physicists and philosophers of science may be particularly interested in chapters 3, 4, and 7. These chapters taken together constitute a detailed examination of Bohr’s philosophy-physics and offer a coherent reconstruction of the interpretative issues together with an accessible and systematic presentation of some important experimental results from the past decade. (Barad 2007:37)

Chapter 5 was originally published as a journal article, and I have retained its original structure so that it can continue to be usefully read as a separate stand-alone piece. Conversely, it could conceivably be skipped without losing the continuity of the argument (though surely risking some important insights). (Barad 2007:37)

Chapter 4 is a key chapter. And in many respects so is chapter 7 (this is where the notion of ‘‘entanglement’’ takes on important nuances, textures, and crucial noncolloquial meanings). Less scientifically inclined readers, or readers who may think of themselves as not very interested in the details of the philosophical issues in quantum physics, may be tempted to skip chapter 7. I would like to encourage at least a cursory reading of this chapter, if only for its valuable insights into the nature of causality, identity, and nature. (Barad 2007:37-8)


I had the privilege of watching as an STM (scanning tunneling microscope) operator zoomed in on a sample of graphite, and as we approached a scale of thousands of nanometers . . . hundreds of nanometers . . . tens of nanometers . . . down to fractions of a nanometer, individual carbon atoms were imaged before our very eyes. The experience was so sublime that it sent chills through my body—and I stood there, a theoretical physicist who, like most of my kind, rarely ventures into the basements of physics buildings that experimental colleagues call “home,” conscious that this was one of those life moments when the amorphous jumble of history seems to crystallize in a single instant. How many times had I recounted for my students the evidence for the existence of atoms? And there they were — just the right size and grouped in a hexagonal structure with the interatomic spacings as predicted by theory. “If only Einstein, Rutherford, Bohr, and especially Mach could have seen this!” I exclaimed. (Barad 2007:39)

CONSTRUCIONISMO (epistem-ont-ologia)

[A]s constructivists have tried to make clear, empirical adequacy is not an argument that can be used to silence charges of constructivism. The fact that scientific knowledge is constructed does not imply that science doesn’t “work,” and the fact that science “works” does not mean that we have discovered human-independent facts about nature. (Of course, the fact that empirical adequacy is not proof of realism is not the endpoint, but the starting point, for constructivists, who must explain how it is that such constructions work — an obligation that seems all the more urgent in the face of increasingly compelling evidence that the social practice of science is conceptually, methodologically, and epistemologically allied along particular axes of power.). (Barad 2007:40)

What is needed is a deeper understanding of the ontological dimensions of scientific practice. It is crucial that we understand the technologies by which nature and culture interact. (Barad 2007:42)


Shifting the focus in studies of science away from the traditional emphasis on theory construction to the examination of experimental practice, Hacking grounds his position on the ability of the experimenter to manipulate entities in the laboratory. That which exists is that which we can use to intervene in the world to affect something else: electrons are counted as real because they are effective experimental tools, not because they have been “found”. (Barad 2007:41)

The philosopher Ian Hacking uses manipulability — that is, the ability to intervene effectively — as the criterion for determining what is real. Hacking claims that whatever individual experimental physicists might believe about whether scientific theories are true accounts of the world or simply useful models for thinking with, it wouldn’t make sense for them to be anything but realists toward the entities that they use as tools: “Experimenting on an entity does not commit you to believing that it exists. Only manipulating an entity, in order to experiment on something else, need do that. . . . [For example,] electrons are no longer ways of organizing our thoughts or saving the phenomena that have been observed. They are now ways of creating phenomena in some other domain of nature. Electrons are tools” (Hacking 1983, 263). Thus Hacking spells out his criterion as follows: “We shall count as real what we can use to intervene in the world to affect something else, or what the world can use to affect us” (146). […] Reflection is insufficient; intervention is key: “Don’t just peer, interfere” (189). (Barad 2007:50)


Latour (1993) prioritizes stability […], posing it as one variable of a two-dimensional geometry whose other axis connects the poles of Nature and Society. Essence thus becomes the trajectory of stabilization within this geometry that is meant to characterize the variable ontologies of quasi-objects. In contrast, Haraway (1988) emphasizes instability: it is the instability of boundaries defining objects that is the focal point of her explicit challenge not only to conceptions of nature that claim to be outside of culture, but also to the separation of epistemology from ontology. The instability of boundaries and Haraway’s insistence that the objects of knowledge are agents in the production of knowledge feature her notions of cyborgs (1985) and material-semiotic actors (1988), which strike up dissonant and harmonic resonances with Latour’s hybrids and quasi-objects (1993). (Barad 2007:41)


Liberal social and political theories and theories of scientific knowledge alike owe much to the idea that the world is composed of individuals — presumed to exist before the law, or the discovery of the law — awaiting or inviting representation. The idea that beings exist as individuals with inherent attributes, anterior to their representation, is a metaphysical presupposition that underlies the belief in political, linguistic, and epistemological forms of representationalism. Or to put the point the other way around, representationalism is the belief in the ontological distinction between representations and that which they purport to represent; in particular, that which is represented is held to be independent of all practices of representing. That is, there are assumed to be two distinct and independent kinds of entities — representations and entities to be represented. The system of representation is sometimes explicitly theorized in terms of a tripartite arrangement. For example, in addition to knowledge (i.e., representations), on the one hand, and the known (i.e., that which is purportedly represented), on the other, the existence of a knower (i.e., someone who does the representing) is sometimes made explicit. When this happens, it becomes clear that representations are presumed to serve a mediating function between independently existing entities. This taken-for-granted ontological gap generates questions of the accuracy of representations. For example, does scientific knowledge accurately represent an independently existing reality? Does language accurately represent its referent? Does a given political representative, legal counsel, or piece of legislation accurately represent the interests of the people allegedly represented?. (Barad 2007:46-7)

Critical examination of representationalism did not emerge until the study of science shifted its focus from the nature and production of scientific knowledge to the study of the detailed dynamics of the actual practice of science. This significant shift is one way to coarsely characterize the difference in emphasis between separate disciplinary studies of science (e.g., history of science, philosophy of science, sociology of science) and science studies. (Barad 2007:47)

representationalism is a practice of bracketing out the significance of practices; that is, representationalism marks a failure to take account of the practices through which representations are produced. Images or representations are not snapshots or depictions of what awaits us but rather condensations or traces of multiple practices of engagement. (Barad 2007:53)

Representationalism and Newtonian physics have roots in the seventeenth century. The assumption that language is a transparent medium that transmits a homologous picture of reality to the knowing mind finds its parallel in a scientific theory that takes observation to be the benign facilitator of discovery, a transparent lens passively gazing at the world. Just as words provide descriptions or representations of a preexisting reality, observations reveal preexisting properties of an observation-independent reality. In the twentieth century, both the representational or mimetic status of language and the inconsequentiality of the observational process have been called into question. (Barad 2007:97)


Performative approaches call into question representationalism’s claim that there are representations, on the one hand, and ontologically separate entities awaiting representation, on the other, and focus inquiry on the practices or performances of representing, as well as the productive effects of those practices and the conditions for their efficacy. A performative understanding of scientific practices, for example, takes account of the fact that knowing does not come from standing at a distance and representing but rather from a direct material engagement with the world. Importantly, what is at issue is precisely the nature of these enactments. Not any arbitrary conception of doings or performances qualifies as performative. And humans are not the only ones engaged in performative enactments (which are not the same as theatrical performances). (Barad 2007:49)

What may seem evident to some is not simply a result of how things are independently of specific practices of seeing and other bodily engagements with the world. Rather, it has become increasingly clear that the seemingly self-evidentiary nature of bodily boundaries, including their seeming visual self-evidence, is a result of the repetition of (culturally and historically) specific bodily performance. (Barad 2007:155)


Social, technological, and scientific practices that included the entangled apparatuses of colonial conquest, democracy, world citizenship, antianarchism, trains, telegraphs, clocks, and other electromechanical devices composed of wires and gears all played a role in the production of the special theory of relativity. […] Time isn’t an abstract idea for Einstein; time is what we measure with a clock. […] [I]deas that make a dfference in the world don’t fly about free of the weightiness of their material instantiation. To theorize is not to leave the material world behind and enter the domain of pure ideas where the lofty space of the mind makes objective reflection possible. Theorizing, like experimenting, is a material practice.(Barad 2007:55)

[T]heory and experiment are […] seen as dynamic practices of material engagement with the world. (Barad 2007:55)

[A]pparatuses provide the conditions for the possibility of determinate boundaries and properties of ‘‘objects’’ within phenomena, where “phenomena” are the ontological insep- arability of objects and apparatuses. (Barad 2007:110)

In the absence of a given apparatus there is no unambiguous way to differentiate between the object and the agencies of observation: an apparatus must be introduced to resolve the ambiguity, but then the apparatus must be understood as part of what is being described. (Barad 2007:118)

In Bohr’s account, objectivity requires accountability to “permanent marks—such as a spot on a photographic plate, caused by the impact of an electron—left on the bodies which define the experimental conditions” (Barad 2007:120)

According to Bohr, theoretical concepts (e.g., position and momentum) are not ideational in character but rather specific physical arrangements. For example, the notion of position cannot be presumed to be a well-defined abstract concept; nor can it be presumed to be an individually determinate attribute of independently existing objects. Rather, position has meaning only when an apparatus with an appropriate set of fixed parts is used. And furthermore, any measurement of position using this apparatus cannot be attributed to some abstract, independently existing object but rather is a property of the phenomenon — the inseparability of the object and the measuring agencies. Similarly, momentum is meaningful only as a material arrangement involving a specific set of movable parts. Hence the indeterminacy of simultaneous position and momentum measurements is a straightforward matter of the material exclusion of position and momentum arrangements (one requiring fixed parts, and the complementary arrangement requiring those same parts to be movable). (Barad 2007:139)

[A]pparatuses are specific material reconfigurings of the world that do not merely emerge in time but iteratively reconfigure spacetimematter as part of the ongoing dynamism of becoming. (Barad 2007:142)

According to Bohr, apparatuses are macroscopic material arrangements through which particular concepts are given definition, to the exclusion of others, and through which particular phenomena with particular determinate physical properties are produced. (Barad 2007:142)

Bohr insists that only concepts defined by their specific embodiment as part of the material arrangement—which includes instrumentation (e.g., photographic plates, pointers, or digital readout devices) that marks definite values of the specifically defined proper- ties and can be read by a human observer—are meaningful. That is, the larger material arrangement enacts a cut that resolves the inherent ontic-semantic indeterminacy through which the “subject” and the “object” emerge. (Barad 2007:142)

My agential realist elaboration of apparatuses entails the following significant developments beyond Bohr’s formulation: (1) apparatuses are specific material-discursive practices (they are not merely laboratory setups that embody human concepts and take measurements); (2) apparatuses produce differences that matter — they are boundary-making practices that are formative of matter and meaning, productive of, and part of, the phenomena produced; (3) apparatuses are material configurations/dynamic reconfigurings of the world; (4) apparatuses are themselves phenomena (constituted and dynamically reconstituted as part of the ongoing intra-activity of the world); (5) apparatuses have no intrinsic boundaries but are open-ended practices; and (6) apparatuses are not located in the world but are material configurations or reconfigurings of the world that re(con)figure spatiality and temporality as well as (the traditional notion of) dynamics (i.e., they do not exist as static structures, nor do they merely unfold or evolve in space and time). (Barad 2007:146)

For Bohr, apparatuses are particular physical arrangements that give meaning to certain concepts to the exclusion of others; they are the local physical conditions that enable and constrain knowledge practices such as conceptualizing and measuring; they are productive of (and part of ) the phenomena produced; they enact a local cut that produces “objects” of particular knowledge practices within the particular phenomena produced. (Barad 2007:146)

[A]pparatuses are discursive practices, where the latter are understood as specific material reconfigurings through which “objects” and “subjects” are produced. (Barad 2007:148)

Apparatuses enact agential cuts that produce determinate boundaries and properties of “entities” within phenomena, where “phenomena” are the ontological inseparability of agentially intra-acting components. That is, agential cuts are at once ontic and semantic. It is only through specific agential intra-actions that the boundaries and properties of “components” of phenomena become determinate and that particular articulations become meaningful. In the absence of specific agential intra-actions, these ontic-semantic boundaries are indeterminate. In short, the apparatus specifies an agential cut that enacts a resolution (within the phenomenon) of the semantic, as well as ontic, indeterminacy. Hence apparatuses are boundary-making practices. (Barad 2007:148)

He explains complementarity by considering two mutually exclusive ways for a person in a dark room to usefully intra-act with a stick or cane: one possibility is for the person to use the stick to negotiate his way around the room by holding the stick firmly in his hands, in which case the stick is properly understood to be part of the “subject,” or he can instead choose to hold the stick loosely to sense its features, in which case the stick is the “object” of observation […] [.] The mutual exclusivity of these two different practices is evident. The stick cannot usefully serve as an instrument of observation if one is intent on observing it. The line between subject and object is not fixed, but once a cut is made (i.e., a particular practice is being enacted), the identification is not arbitrary but in fact materially specified and determinate for a given practice. (Barad 2007:154-5)


Gendering, Butler argues, is a temporal process that operates through the reiteration of norms. In other words, Butler is saying that gender is not an inherent feature of individuals, some core essence that is variously expressed through acts, gestures, and enactments, but an iterated doing through which subjects come into being. But these are precisely the kinds of points that one would think that actor network theorists and other scholars attuned to looking for ways in which “objects” emerge through scientific practices would be especially attentive to. And yet there has been surprisingly little cross-pollination between feminist post-structuralist theory and science studies. Even in the feminist science studies literature, one is hard pressed to find direct engagements with Butler’s work on performativity. (Barad 2007:57)

[M]ainstream science studies scholars seem to be unaware of the fact that the nature-culture dichotomy has been challenged vigorously on multiple grounds by feminist, poststructuralist, postcolonialist, queer, and other critical social theorists, and that attending to the issues they raise is an integral part of questioning the constitution of the nature-culture dichotomy and the work it does: not only that it matters, but how it matters and for whom. (Barad 2007:57)

[T]he notions of objects, space, size, distance, and depth cannot be assumed to take on the same meanings for sighted and blind people. Clearly, we do not see merely with our eyes. Interacting with (or rather, intra-acting “with” and as part of) the world is part and parcel of seeing. Objects are not already there; they emerge through specific practices.(Barad 2007:157)


[A]s Butler and Bohr emphasize, that which is excluded in the enactment of knowledge-discourse-power practices plays a constitutive role in the production of phenomena — exclusions matter both to bodies that come to matter and those excluded from mattering. (Barad 2007:57)


What conception of power, what model of citizenship, what immigration policy is being enacted when a new representationalist democracy is being proposed that only acknowledges two kinds of citizens and their offspring—the fully human (those who had already been granted citizenship) and the fully nonhuman and their hybrids? (Barad 2007:59)


Any proposal for a new political collective must take account of not merely the practices that produce distinctions between the human and the nonhuman but the practices through which their differential constitution is produced. (Barad 2007:59)


As Haraway (1997) correctly points out, Foucault’s notion of the biopolitical field is seriously outdated and incapable of taking account of the new technoscientific practices that continually rework the boundaries between the “human” and the “nonhuman.” (Barad 2007:65)


Crucial to understanding the workings of power is an understanding of the nature of power in the fullness of its materiality. To restrict power’s productivity to the limited domain of the social, for example, or to figure matter as merely an end product rather than an active factor in further materializations is to cheat matter out of the fullness of its capacity. How might we understand not only how human bodily contours are constituted through psychic processes but also how even the very atoms that make up the biological body come to matter, and more generally how matter makes itself felt? It is difficult to imagine how psychic and sociohistorical forces alone could account for the production of matter. Surely it is the case […] that there are “natural,” not merely “social,” forces that matter. Indeed, there is a host of material-discursive forces—including ones that get labeled “social,” “cultural,” “psychic,” “economic,” “natural,” “physical,” “biological,” “geopolitical,” and “geological” — that may be important to particular (entangled) processes of materialization. (Barad 2007:66)


Measurement is a meeting of the “natural” and the “social.” It is a potent moment in the construction of scientific knowledge — it is an instance where matter and meaning meet in a very literal sense. This is one reason why science studies scholars have been interested in studying the role of detectors (in high energy physics) — they are sites for making meaning (Traweek 1988; Galison 1987; Pickering 1984). (Barad 2007:67)

EMARANHADOS (entanglements)

What is entailed in the investigation of entanglements? How can one study them? Is there any way to study them without getting caught up in them? What can one say about them? Are there any limits to what can be said? My purpose is not to make general statements as if there were something universal to be said about all entanglements, nor to encourage analogical extrapolation from my examples to others, nor to reassert the authority of physics. On the contrary, I hope my exploration will make clear that entanglements are highly specific configurations and it is very hard work building apparatuses to study them, in part because they change with each intra-action. In fact it is not so much that they change from one moment to the next or from one place to another, but that space, time, and matter do not exist prior to the intra-actions that reconstitute entanglements. Hence, it is possible for entangled relationalities to make connections between “entities” that do not appear to be proximate in space and time. […] The point is that the specificity of entanglements is everything. The apparatuses must be tuned to the particularities of the entanglements at hand. The key question in each case is this: how to responsibly explore entanglements and the differences they make. (Barad 2007:74)


Classically speaking, particles are material entities, and each particle occupies a point in space at a given moment of time. Waves, on the other hand, are not things per se; rather, they are disturbances (which cannot be localized to a point) that propagate in a medium (like water) or as oscillating fields (like electromagnetic waves, the most familiar example being light). Unlike particles, waves can overlap at the same point in space. When this happens, their amplitudes combine to form a composite waveform. (Barad 2007:76)

Crucially, diffraction patterns mark an important difference between waves and particles: according to classical physics, only waves produce diffraction patterns; particles do not (since they cannot occupy the same place at the same time). Indeed, a diffraction grating is simply an apparatus or material configuration that gives rises to a superposition of waves. In contrast to reflecting apparatuses, like mirrors, which produce images — more or less faithful — of objects placed a distance from the mirror, diffraction gratings are instruments that produce patterns that mark differences in the relative characters (i.e., amplitude and phase) of individual waves as they combine. […] So unlike the phenomenon of reflection, which can be explained without taking account of the wavelike behavior of light (i.e., it can be explained using an approximation scheme called “geometrical optics” whereby light might well be a particle that bounces off surfaces), diffraction makes light’s wavelike behavior explicit (i.e., it can only be accounted for by using the full theory of “physical optics”). (Barad 2007:81)

Before the early years of the twentieth century, it seemed that everything could be sorted neatly into the distinct categories of waves and particles. Each “bit” of nature had a distinct identity that landed it a place in one column or the other. After all, waves and particles are distinct phenomena with mutually exclusive characteristics. Particles are localized objects that occupy a given location at each moment in time. Waves have an entirely different nature: they are not even properly entities but rather disturbances in some medium or field. Waves have extension in space, occupying more than one position at any moment of time, like ocean waves that move along a stretch of beach; and furthermore, waves can overlap (i.e., interfere) with one another and occupy the same position at any moment of time, unlike particles. The dual nature of light and matter presented a quandary of the first order: an object is either localized or extended; it can’t be both. (Barad 2007:100)

For Bohr, the crucial point is the fact that wave and particle behaviors are exhibited under complementary — that is, mutually exclusive — circumstances. According to Bohr, either we can find out which slit an electron goes through by using the which-path apparatus, in which case the resulting pattern will be that which characterizes particles, or we can forgo knowledge about which path the electron goes through (using the original unmodified two-slit apparatus) and obtain a wave pattern — we can’t have it both ways at once. (Barad 2007:106)

Crucially, then, the position and momentum are not simultaneously determinate because they require mutually exclusive experimental cir- cumstances (a fixed support and a movable support respectively; see figure 12). (Barad 2007:111)

Bohr resolves the wave-particle duality paradox as follows: “wave” and “particle” are classical concepts (that are given determinate meanings by different, indeed mutually exclusive, apparatuses and) that refer to different, mutually exclusive phenomena, not to independent physical objects. He emphasized that this saved the theory from inconsistencies, since it was impossible to observe particle and wave behaviors simultaneously because mutually exclusive experimental arrangements are required. (Barad 2007:121)


The ray approximation of geometrical optics works well when the wavelength of light is small compared with the physical dimensions of the objects it is interacting with, such as the size of a slit that the light passes through. If the wavelength is small compared with the slit size, then diffraction effects such as the bending of light will be too small to be noticeable. However, when the wavelength is approximately the same size as the slit or larger, then diffraction effects (i.e., the wave nature of light) cannot be ignored. Hence when the wavelength of light is approximately the same size as, or larger than, the object it encounters (e.g., sizable in comparison to the width of the slits), the techniques of physical optics — the full mathematical machinery that is attentive to the wave nature of light — must be used to correctly account for the phenomenon. In effect, then, geometrical optics is merely a shortcut way of deriving the correct results when the wavelength happens to be small enough compared to other relevant dimensions in the experiment. (Barad 2007:85)


The crux of the analogy is this: when in the case of a particular experiment the wave nature of light or matter is not significant (i.e., when the wavelength is small relative to other important dimensions), it may be possible to use classical mechanics (geometrical optics) as a shortcut to the more rigorous analysis that quantum mechanics (physical optics) provides. So whereas classical mechanics and geometrical optics are (nowadays understood to be) approximation schemes that are useful under some circumstances, quantum mechanics and physical optics are understood to be formalisms that represent the full theory and can account for phenomena at all length scales. Significantly, quantum mechanics is not a theory that applies only to small objects; rather, quantum mechanics is thought to be the correct theory of nature that applies at all scales. As far as we know, the universe is not broken up into two separate domains (i.e., the microscopic and the macroscopic) identified with different length scales with different sets of physical laws for each. (Barad 2007:85)


[W]e don’t notice the furniture being rearranged in the room when we turn a light on in a dark room, although this is strictly the case. […] There are, however, situations in which the disturbance is noticeable (e.g., when the accuracy of the measurement is increased beyond a certain limit or when the object is sufficiently small). (Barad 2007:108)


Second, causality is too often conceptualized as a binary affair: either a situation of strict determinism applies (i.e., causal determination) or there is a state of freedom (i.e., no causal determination). However, there are more ways to think about causal relations than the usual choices between determinism and free will (as Bohr specially mentions). Since traditional formulations of causality assume that independently determinate entities precede some causal interaction, we are clearly already on very new ground. Third, the fact that scientific results are reproducible requires (or at least seems to require) that intra-actions entail some kind of causal structure—that is, something being the cause, and something the effect—otherwise it would be impossible (or at least very difficult) to account for the reproducibility of experiments. (Barad 2007:131)


What compels the belief that we have a direct access to cultural representations and their content that we lack toward the things represented? How did language come to be more trustworthy than matter? Why are language and culture granted their own agency and historicity, while matter is figured as passive and immutable or at best inherits a potential for change derivatively from language and culture? (Barad 2007:132)

Nietzsche warned against the mistaken tendency to take grammar too seriously: allowing linguistic structure to shape or determine our understanding of the world, believing that the subject-and-predicate structure of language reflects a prior ontological reality of substance and attribute. The belief that grammatical categories reflect the underlying structure of the world is a continuing seductive habit of mind worth questioning. (Barad 2007:133)


performativity is properly understood as a contes- tation of the unexamined habits of mind that grant language and other forms of representation more power in determining our ontologies than they deserve. (Barad 2007:133)


Representationalism, metaphysical individualism, and humanism work hand in hand, holding this worldview in place. These forces have such a powerful grip on contemporary patterns of thought that even some of the most concerted efforts to escape the grasp of these anthropocentric forces have failed. (Barad 2007:134)


Difference cannot be taken for granted; it matters—indeed, it is what matters. The world is not populated with things that are more or less the same or different from one another. Relations do not follow relata, but the other way around. Matter is neither fixed and given nor the mere end result of different processes. Matter is produced and productive, generated and generative. Matter is agentive, not a fixed essence or property of things. Mattering is differentiating, and which differences come to matter, matter in the iterative production of different differences. Changing patterns of difference are neither pure cause nor pure effect; indeed, they are that which effects, or rather enacts, a causal structure, differentiating cause and effect. Difference patterns do not merely change in time and space; spacetime is an enactment of differentness, a way of making/marking here and now. (Barad 2007:136-7)


Representationalism takes the notion of separation as foundational. It separates the world into the ontologically disjunct domains of words and things, leaving itself with the dilemma of their linkage such that knowledge is possible. If words are untethered from the material world, how do representations gain a foothold? If we no longer believe that the world is teeming with inherent resemblances whose signatures are inscribed on the face of the world, things already emblazoned with signs, words lying in wait like so many pebbles of sand on a beach there to be discovered, but rather that the knowing subject is enmeshed in a thick web of representations such that the mind cannot see its way to objects that are now forever out of reach and all that is visible is the sticky problem of humanity’s own captivity within language, then it becomes apparent that representationalism is a prisoner of the problematic metaphysics it postulates. Like the frustrated would-be runner in Zeno’s paradox, representationalism never seems to get any closer to solving the problem it poses because it is caught in the impossibility of stepping outward from its metaphysical starting place. What is needed is a new starting place. (Barad 2007:137)


Unfortunately Bohr does not explore the crucial ontological dimensions of his insights but rather focuses on their epistemological import. I have mined his writings for his implicit ontological views (see chapter 3) and here elaborate on them in the development of an agential realist ontology. (Barad 2007:138)

DISCURSO (Foucault)

Discourse is not what is said; it is that which constrains and enables what can be said. Discursive practices define what counts as meaningful statements. (Barad 2007:146)


Knowing is a matter of intra-acting. (Barad 2007:149)

. (Barad 2007:)

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