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Consciousness as Intrinsic Structure: Towards a Chemistry of Experience
Matteo Grasso, Jeremiah Hendren, Giulio Tononi
TL;DR
The paper asks how conscious contents can be explained as structured phenomenal wholes rather than collections of atoms. It applies IIT’s Φ-structure framework to spatial extendedness, temporal flow, and objects, demonstrating a chemistry-like account and predicting content changes when substrate structure changes.
Problem
The paper addresses how conscious contents, which form structured wholes of distinctions and relations, can be characterized and explained scientifically.
Method
The paper applies IIT’s axioms and postulates to identify a substrate’s complex and unfold its cause–effect power into a Φ-structure.
Results
The paper demonstrates accounts of spatial extendedness, temporal flow, and objects while outlining chemistry-like principles for explaining diverse experience contents.
Takeaways & Limitations
The framework predicts that altering a substrate’s specified structure should alter corresponding experience content even when activity and behavior remain comparable.
Takeaways & Limitations
The demonstrated accounts cover basic introspectively decomposable contents, while complex compound contents and narrow qualia remain an open research program.
Abstract
from arXiv · showhide
To be conscious is to have an experience - not a collection of phenomenal atoms, but a structured whole composed of distinctions and the relations that bind them. Integrated Information Theory (IIT) identifies the essential properties of every experience (axioms), formulates them operationally as postulates that a substrate must satisfy, and unfolds the cause-effect power of the resulting complex into a $Φ$-structure. Accounting for a content of experience is then a matter of identifying the phenomenal distinctions and relations that compose it, and showing them reflected one-to-one in the causal distinctions and relations of the corresponding $Φ$-structure. We apply that method to three pervasive contents whose structure is partly open to introspection. Spatial extendedness is composed of spots, whose elemental signature is reflexivity, bound by reflexive inclusion, connection, and fusion; temporal flow is composed of moments, whose signature is directedness, bound by directed inclusion, connection, and fusion; objects bind a particular configuration of features to a general concept through relations bearing the signature of hierarchy. The endeavor is akin to chemistry, which accounts for an endless variety of compounds from a limited set of elements and the ways they bond. We assess these accounts against seven criteria of a good explanation - scope, synthesis, specificity, self-consistency, system consistency, simplicity, and scientific validation - and sketch the prediction that follows: altering the structure specified by a substrate should alter the corresponding content, even when activity and behavior are held comparable. The same method may reach narrow qualia, which resist introspection, and the compound contents that bind many qualia together, though there it remains a proof of concept and an open research program.
1. Introduction
The introduction presents experience as an intrinsic phenomenal structure of distinctions and binding relations, and IIT’s aim as identifying its corresponding causal Φ-structure. It frames content explanation as a chemistry-like account that composes diverse experiences from limited building blocks and relations.
- IIT treats each experience as an intrinsic phenomenal structure composed of phenomenal distinctions and the relations that bind them.The structure characterizes the quality of experience and differentiates one experience or content from another.
- IIT seeks to explain phenomenal structure scientifically as a Φ-structure specified by a substrate’s operational cause–effect power.It formulates axioms of phenomenal existence as postulates of physical existence.
- IIT explains contents by identifying their building blocks and binding relations, analogous to chemistry’s composition of varied compounds from limited elements and bonds.This approach aims to account for an immense variety of contents from relatively few kinds of distinctions and relations.
- The chapter demonstrates this method for spatial extendedness, temporal flow, and the conceptual hierarchy characterizing objects, then generalizes toward a chemistry of experience.Its broader aim is to develop a self- and system-consistent way to characterize contents of experience.
2. Where do we start
IIT begins a chemistry of experience with simple, pervasive contents whose structure is partly open to introspection: spatial extendedness, temporal flow, and objects. It identifies their elemental components, signatures, and binding relations as a basis for explaining more complex contents.
- Method: The proposed method first identifies a content’s building blocks and elemental signature, then explains how characteristic relations combine them into a phenomenal compound.This mirrors chemistry’s explanation of compounds through elements and bonding relations.
- Motivation: IIT treats spatial extendedness, temporal flow, and objects as qualia themselves, not merely neutral stages for other experiences.Without spatial structure, colors would not appear laid out; without temporal flow, melodies would lack ordered moments.
- Method: These contents are promising starting points because their rich internal structure can be partially inspected, decomposed, and recombined from within.One can resolve regions into spatial parts, moments into shorter periods, and marks into familiar objects.
- Contribution: Spatial extension is composed of spots with reflexive signatures, combined by reflexive inclusion, connection, and fusion; temporal flow similarly begins with moments but has a different signature.The passage introduces spots and moments as the elemental components of space and time, respectively.
- Scope: Validating these explanatory identities empirically would support IIT’s characterization of consciousness as intrinsic structure and extend the program toward less introspectable qualia.Narrow qualia may require stronger reliance on inferences from properties of the Φ-structure.
3. Space, time, and objects in a nutshell
IIT analyzes space, time, and objects by identifying their phenomenal elements and relations, then matching them to causal distinctions and relations in substrates. Spots with reflexivity compose spatial extension, moments with directedness compose temporal flow, and hierarchical configurations and concepts compose objects.
- Method: IIT’s common method starts by identifying each content’s phenomenal elements and binding relations, then asking which causal distinctions, relations, and substrates can mirror them.The method proceeds from phenomenological analysis to a causal formulation and substrate specification.
- Space: Spatial extendedness is composed of spots whose elemental signature is reflexivity, bound through reflexive inclusion, connection, and fusion.A spot’s causal distinction is specified by units whose receptive fields cover its region, while these relations organize spots into extended space.
- Time: Temporal flow is composed of moments whose elemental signature is directedness, with inclusion, connection, and fusion relating moments into extended periods.Directedness corresponds causally to a distinction whose cause and effect are over different units, toward the now and the then.
- Objects: Objects are hierarchical compounds that bind particular feature configurations to general concepts, with configurations and concepts linked through hierarchical inclusion, connection, and fusion.In visual experience, this binding makes features such as a color belong to a letter, word, or other recognizable whole; the account remains under development.
4. A good explanation?
The proposed chemistry of experience applies a common method to diverse contents by identifying distinctions, signatures, and bonds, and evaluates the resulting explanation through seven criteria. Its scientific test is that altering a substrate’s Φ-structure should alter experience even when activity and behavior remain comparable.
- Method: The method accounts for contents as Φ-folds built from elemental distinctions, signatures, and bonds, extending one compositional framework across space, time, and objects.The initial accounts identify reflexivity, directedness, or hierarchy as signatures, with corresponding inclusion, connection, and fusion bonds.
- Evaluation: The seven criteria of a good explanation are scope, synthesis, specificity, self-consistency, system consistency, simplicity, and scientific validation.Together, these criteria distinguish an explanatory chemistry of experience from a catalogue that merely lists contents.
- Evaluation: IIT seeks synthesis and simplicity by explaining diverse contents through intrinsic structure and five essential properties translated into causal terms by the postulates.The same principles apply across space, time, and objects while preserving their structural differences.
- Specificity: Specificity requires one-to-one mappings in which changes to causal distinctions or relations produce corresponding changes in experiential content.For spatial experience, the proposed structure must explain the felt location, size, boundary, and distance relations of spots.
- Scientific validation: Scientific validation predicts that changing a content’s Φ-structure should change that content even when activity and behavior are held comparable.The account must also connect phenomenology with causal and neural organization and cohere with the broader scientific picture.
- Scientific validation: The framework generates testable predictions for consciousness and its contents, including corticothalamic dependence, distortions of spatial distance, temporal scaling with directed grids, and selective disruption of object experience.These predictions distinguish an explanatory chemistry from a periodic-table-like inventory of experiential contents.
5. Where do we go from here
The method may extend from introspectively decomposable contents to narrow qualia and complex compound contents, but these applications remain largely a proposed research direction. Narrow qualia require inferring experience from substrate structure, while compound contents demand accounts of far more complex phenomenal organizations.
- Scope and outlook: Thus far, the demonstrated accounts concern contents whose structure can at least partly be decomposed through introspection, whereas richer narrow and compound qualia remain beyond the current demonstrations.The paper characterizes extending the method to these contents as a direction proposed by IIT rather than an accomplished account.
- Narrow qualia: Narrow qualia are hardest because introspection cannot decompose their qualities into phenomenal distinctions and relations, making them paradigmatic hard-problem cases.We can compare narrow qualia through similarity and difference, but cannot directly introspect their elemental structure.
- Narrow qualia: IIT proposes inferring a narrow quale from its substrate: if explanatory identity holds for space, time, and objects, and all quality is structure, the quale should correspond to intrinsic structure (Tononi & Boly, 2025).The kernel’s elemental signature and bonds remain inaccessible to introspection, so researchers can study the clique of units specifying it and seek interventions that alter the quale.
- Compound contents: The same program could address compound contents such as visual motion, bodily and worldly multimodal space, emotions, thoughts, and the sense of self, which are more complex than basic components (Tononi & Boly, 2025).These contents resemble complex compounds rather than simple atoms or molecules, but the passage presents them as an open extension of the approach.
IIT in a box
IIT explains consciousness in objective physical terms by identifying a substrate’s irreducible cause–effect power and equating the resulting Φ-structure with experience. Its quantity corresponds to integrated information, while its quality corresponds to the structure of that Φ-structure, with empirical validation proceeding through introspective reports and predicted brain-substrate properties.
- Aim: IIT aims to explain both why experience exists and why particular experiences feel as they do in objective, physical terms.These are IIT’s two guiding questions about consciousness.
- Method: IIT begins with experience as an undeniable fact, derives axioms describing every experience as intrinsic, specific, unitary, definite, and structured, and translates them into physical postulates.The method is “consciousness first” and uses introspection to identify phenomenal properties before formulating their operational physical counterparts.
- Method: Applying the postulates identifies a complex whose cause–effect power upon itself is maximally irreducible, then unfolds that power into a Φ-structure of causal distinctions and relations.The complex is the substrate of consciousness.
- Central claim: IIT’s central claim is an explanatory identity between experience and the substrate’s Φ-structure: integrated information determines consciousness quantity, while Φ-structure determines quality.On this view, all quality is structure; essential experiential properties are captured by the postulates, while contents such as space, time, and objects arise from the Φ-structure’s composition.
- Validation: Empirical validation starts with introspective human reports and tests whether brain anatomy and physiology support the predicted complexes and Φ-structures across conscious and unconscious states.IIT has been applied to consciousness dependence on some brain regions, fading during dreamless sleep and anesthesia, and returning during waking and dreaming.