Definition
“Cut” in this record means one of the following, and a claim should say which.
- Cartesian cut. A separation of subject from object, or observer from observed, taken as fixed before any measurement and independent of it. It is Barad’s name for what she rejects (A6 §2: “the subject/object distinction is treated as antecedent and ontologically fixed”).
- Epistemic cut (Pattee). The separation of symbol from referent, description from dynamics, controller from controlled, which dynamical laws cannot describe without losing the function across it. Measurement codes a rate-dependent state into rate-independent symbols, and control is its converse; both are executed by non-integrable constraints. Pattee holds the cut epistemic, not ontological (LIT-1190, read in NOTE-952).
- Agential cut (Barad). A differentiation enacted within a phenomenon, through which some boundaries and properties become determinate and others are excluded, so that what functions as measuring agency and what as object are told apart “without requiring these to have been independently individuated in advance” (A6 §2). Barad’s own words, in the one text of hers read here (LIT-1869, NOTE-1458): “A specific intra-action enacts an agential cut (in contrast to the Cartesian cut – an inherent distinction – between subject and object) effecting a separation between “subject” and “object”. That is, the agential cut enacts a “local” resolution within the phenomenon of the inherent ontological indeterminacy” (2012, p. 32). The result is agential separability, “exteriority-within-phenomena”: real but not absolute separation. What enacts it is an apparatus, in Barad’s sense not an instrument but “an open-ended, dynamic configuration of material practices through which particular differences become real and intelligible”, itself a phenomenon and itself reconfigured (A6 §1). Barad’s own words, as Faye and Jaksland quote them: “apparatuses are the material conditions of possibility and impossibility of mattering; they enact what matters and what is excluded from mattering” (Barad 2007, 148; NOTE-1220). The cut is ontological on Barad’s account, and it is movable: “no agential cut is an inherent distinction” (Barad 2007, 140, as Jaksland gives it; NOTE-1230). It is the Heisenberg cut, movable as Heisenberg held against Bohr, made ontological: Jaksland glosses it as “more commonly known as a Heisenberg cut” (p. 367), and Faye and Jaksland note that a movable separation of object and apparatus is “a view that Heisenberg advocates in opposition to Bohr”. Of Barad’s texts only the 2012 essay is read here. It confirms the cut, intra-action and agential separability in her words, but uses “apparatus” only of the two-slit set-up and says nothing of the cut’s movability or of Heisenberg; those parts rest on the exchange’s account and on Faye and Jaksland’s quotations of Barad 2007 (LIT-1657, unavailable).
A9 §4 drew the contrast that makes the term worth having: “Pattee’s epistemic cut is a functional distinction between symbolic description and physical dynamics. Barad’s agential cut is a locally enacted differentiation within a phenomenon. They are not interchangeable concepts. Pattee gives us a clearer mechanism for explaining how descriptions become physically consequential. Barad challenges the idea that the describing and described systems have fundamentally independent identities.”
What it is not
- A partition. A cut in the second or third sense is not any division of a system into parts. A boundary found by a block criterion (CLAIM-157) is a partition; whether it is also an agential cut is QUESTION-284’s question.
- One thing in the record and in physics. CLAIM-476 uses the third sense for a record’s objects only. That a split scheme is an agential cut there says nothing about whether measurement is one.
- Bohr’s separation. Bohr’s own split between object and instrument is, on Faye and Jaksland’s reading, fixed and epistemic, justified by the need for unambiguous classical description, with both relata real (THEORY-1076). It is not the third sense, which is movable and ontological. Whether it is a Cartesian cut in Barad’s sense (the first) is not settled here. The Heisenberg cut, movable, is the third sense’s ancestor (above), and also neighbours the second sense through Pattee’s use of the von Neumann regress.
What would settle it
Adoption by the owner, and a reading of Barad herself that confirms or corrects the third sense. Jaksland 2024 and Faye and Jaksland 2021, read on 2026-10-27, corrected its relation to the Heisenberg cut and supplied Barad’s definition of an apparatus at second hand; the text above is corrected in place, the TERM being unadopted. Barad 2012 (NOTE-1458), read 2026-10-30, confirms the cut in her own words and leaves the apparatus clause and the movability where they were.
Note of 2026-10-30: what holds it back
The core of the agential sense is now confirmed in Barad’s words (2012, p. 32; NOTE-1458). What is not confirmed is that an apparatus enacts the cut, Barad’s definition of an apparatus, and the cut’s movability: these rest only on Faye and Jaksland’s quotations of Barad 2007 (NOTE-1220, NOTE-1230). The 2012 essay says “a specific intra-action enacts an agential cut” and uses “apparatus” only of the two-slit set-up. Those clauses, which CLAIM-476 uses, wait on a reading of LIT-1657.
Note of 2026-10-31: one paper, two senses
Bencherki, Brummans and Vézy (LIT-1902) cite Barad (2003, p. 815) for the agential cut and use it in two senses. At p. 1357: “Describing an action by starting from a human being is but an analytical choice that isolates some aspect in a series of continuous individuation processes; it corresponds to an ‘agential cut’ … or the selection of a link in a chain of agencies”, and so “agency is a matter of perspective”. That is an analyst choosing a description of a process individuated without the choice. It is none of this term’s three senses, and nearest an observer’s choice of coarse-graining. At p. 1366, researchers “can only investigate individuation processes by/while individuating into others”. That is sense 3, a differentiation enacted within a process the analyst belongs to. The paper does not separate the two, and NOTE-1484’s limitation, that perspectivism and realism pull against each other in it, is this ambiguity. A citation of the paper for “agential cut” should say which page it means. No status, title or warrant changes.