Explanatory perspectivalism (Kostić 2014) holds that the hard problem of consciousness arises only for a specific kind of question — how can concepts of subjective experience refer to physical properties? — while questions such as why certain brain states have certain qualities are empirically tractable and should be pursued through topological (network) explanations. The source paper leaves the conceptual core of its own program open: there is still no viable theory of concepts that explains how phenomenal and physical concepts can be co-referential. This problem asks for completion of that core: a theory of phenomenal concepts that explains phenomenal–physical co-reference and withstands the standard anti-physicalist arguments, thereby closing the hard problem in the restricted, conceptual guise in which it survives. Under the source's demarcation, the empirical question about qualities — for which the source commends topological (network) explanation — is tractable independently of this conceptual task and is unimpeded by the restricted hard problem.

Background

Chalmers's 'hard problem' of consciousness (Chalmers 2010) is the problem of explaining why physical processing in the brain gives rise to subjective experience at all — why there is 'something it is like' to see red or feel pain — as opposed to the 'easy problems' of explaining cognitive functions such as attention, report, and behavioral control. A related diagnosis is the explanatory gap: even given complete neural correlations, it seems unintelligible why a given brain state should feel the way it does rather than some other way, or no way at all. Phenomenal concepts are the concepts we exercise when we think about experience from the first-person point of view — for instance, the concept of the visual quality of red deployed when one attends to what red looks like — as opposed to the physical and functional concepts of neuroscience. Physicalists have pursued the phenomenal concept strategy: explain the residual epistemic gap by the special nature of phenomenal concepts (for example, their recognitional or experience-dependent mode of presentation) rather than by a gap in the world (Papineau 2007; Balog 2012). This strategy must answer the co-reference question: how can a phenomenal concept and a physical concept pick out one and the same property, and what explains that convergence when in paradigm cases of scientific identity, such as heat and kinetic energy, there is an explanatory story of why two vocabularies converge? Objections include the knowledge argument (a scientist who knows all the physical facts supposedly learns something new upon first experiencing color), conceivability arguments (that beings physically and functionally identical to us but without experience — 'zombies' — are coherently conceivable), and Chalmers's dilemma for the phenomenal concept strategy, which forces any account of phenomenal concepts either to leave the epistemic gap unexplained or to presuppose the physicalism it was meant to defend (Chalmers 2007); the exchange continues unresolved (Ball 2009; Balog 2012; Levin 2019; Botin 2022; Alter 2023).

Explanatory perspectivalism (Kostić 2014) is the thesis that what we want to know about a phenomenon determines the type of explanation appropriate to understanding it. On this view, the hard problem arises only for questions of the form 'how is it that concepts of subjective experience can refer to physical properties', and not for questions such as what gives rise to qualia (the subjective qualities of experience, such as the particular feel of seeing red as opposed to hearing a trumpet) or why certain brain states have certain qualities and not others, which admit ordinary empirical explanation. Kostić argues that we could in principle fully explain why certain brain processes have certain subjective qualities while still lacking a viable theory of concepts that explains the co-reference of phenomenal and physical concepts; in this restricted, conceptual guise the hard problem remains, but it does not block the empirical study of consciousness.

For the empirical strand, the paper commends topological explanations of the kind developed in network neuroscience: the brain is modeled as a graph whose nodes are regions (or neurons) and whose edges are structural or functional connections, where functional connectivity is typically a synchronization likelihood between activity time series of regions. Standard graph measures include the clustering coefficient (how densely a node's neighbors are interconnected), modularity (the decomposition of the network into densely intra-connected communities), path length (the average shortest route between nodes), and small-world architecture (high clustering combined with short path lengths). Kostić's subsequent work develops this framework: topological realization, in which the realizing base of a phenomenon is a global network property rather than a collection of local components (Kostić 2016), and a general theory of topological explanations and their directionality (Kostić 2020; Kostić and Khalifa 2021), together with an account of when functional-connectivity models genuinely explain (Kostić and Khalifa 2025). A neighboring structural program is integrated information theory (IIT), which identifies consciousness with a system's integrated information and, in its current formulation (Albantakis et al. 2023), claims that the quality of an experience is accounted for by the system's unfolded cause–effect structure (its Φ-structure) — a theoretical identity whose quality predictions are explicitly not yet empirically settled.

Under this demarcation, the semantic question — a viable theory of concepts explaining phenomenal–physical co-reference — is what remains of the hard problem, while the quality-differentiation question is reclassified as an empirical task that perspectivalism predicts can be discharged by topological explanation. Because empirical explanation of why certain brain processes have certain subjective qualities can in principle succeed while the theory of concepts is still lacking, the empirical strand proceeds independently of, and does not gate, the restricted hard problem.

Problem Statement

Complete the research program that explanatory perspectivalism (Kostić 2014) leaves open, whose objective is to close the hard problem of consciousness in the restricted form in which that view leaves it.

Provide a viable theory of concepts that explains how concepts of subjective experience can refer to physical properties: an account of phenomenal concepts on which they can be co-referential with physical concepts (pick out the same properties), precise enough to say what explains that convergence of two prima facie very different vocabularies, and strong enough to withstand the standard anti-physicalist arguments — the knowledge argument, conceivability arguments, and the dilemma formulations pressed against the phenomenal concept strategy (Chalmers 2007; Alter 2023). These requirements are joint and not merely a gloss on 'viable': the account must satisfy all three, and each named anti-physicalist argument must be answered on its own terms, since success against one does not by itself discharge the others.

Under the source's demarcation this conceptual co-reference question is the sole remaining open item: the source reclassifies 'why certain brain states have certain qualities' as empirically tractable — commending topological (network) explanations as the appropriate kind of explanation for it — and holds that, given this limitation, the hard problem does not pose a problem for the empirical study of consciousness. The development and empirical testing of topological models differentiating among types of qualia therefore belong to that independent empirical program which the demarcation frees; they are background to this problem, not a deliverable of it.

References

  1. Kostić, D. (2014). Explanatory Perspectivalism: Limiting the Scope of the Hard Problem of Consciousness. Topoi 36(1):119–125 (first online 2014). DOI: 10.1007/s11245-014-9262-7. https://doi.org/10.1007/s11245-014-9262-7
  2. Chalmers, D. J. (2010). Facing Up to the Problem of Consciousness. In The Character of Consciousness (pp. 3–34). Oxford University Press. DOI: 10.1093/acprof:oso/9780195311105.003.0001. https://doi.org/10.1093/acprof:oso/9780195311105.003.0001
  3. Chalmers, D. J. (2007). Phenomenal Concepts and the Explanatory Gap. In Phenomenal Concepts and Phenomenal Knowledge (pp. 167–194). Oxford University Press. DOI: 10.1093/acprof:oso/9780195171655.003.0009. https://doi.org/10.1093/acprof:oso/9780195171655.003.0009
  4. Papineau, D. (2007). Phenomenal and Perceptual Concepts. In Phenomenal Concepts and Phenomenal Knowledge (pp. 111–144). Oxford University Press. DOI: 10.1093/acprof:oso/9780195171655.003.0007. https://doi.org/10.1093/acprof:oso/9780195171655.003.0007
  5. Balog, K. (2012). In Defense of the Phenomenal Concept Strategy. Philosophy and Phenomenological Research 84(1):1–23. DOI: 10.1111/j.1933-1592.2011.00541.x. https://doi.org/10.1111/j.1933-1592.2011.00541.x
  6. Ball, D. (2009). There Are No Phenomenal Concepts. Mind 118(472):935–962. DOI: 10.1093/mind/fzp134. https://doi.org/10.1093/mind/fzp134
  7. Levin, J. (2019). 'Phenomenal States' and the Scope of the Phenomenal Concepts Strategy. In Sensations, Thoughts, Language (pp. 289–313). Routledge. DOI: 10.4324/9781351017435-14. https://doi.org/10.4324/9781351017435-14
  8. Botin, M. (2022). The Phenomenal Concept Strategy Cannot Explain Problem Intuitions. Journal of Consciousness Studies 29(7):7–31. DOI: 10.53765/20512201.29.7.007. https://doi.org/10.53765/20512201.29.7.007
  9. Alter, T. (2023). The Phenomenal Concept Strategy and Chalmers's Dilemma. In The Matter of Consciousness (pp. 138–153). Oxford University Press. DOI: 10.1093/oso/9780198840459.003.0009. https://doi.org/10.1093/oso/9780198840459.003.0009
  10. Kostić, D. (2012). The Vagueness Constraint and the Quality Space for Pain. Philosophical Psychology 25(6):929–939. DOI: 10.1080/09515089.2011.633696. https://doi.org/10.1080/09515089.2011.633696
  11. Kostić, D. (2016). The Topological Realization. Synthese 195(1):79–98 (first online 2016). DOI: 10.1007/s11229-016-1248-0. https://doi.org/10.1007/s11229-016-1248-0
  12. Kostić, D. (2020). General Theory of Topological Explanations and Explanatory Asymmetry. Philosophical Transactions of the Royal Society B 375(1796):20190321. DOI: 10.1098/rstb.2019.0321. https://doi.org/10.1098/rstb.2019.0321
  13. Kostić, D., and Khalifa, K. (2021). The Directionality of Topological Explanations. Synthese 199:14143–14165. DOI: 10.1007/s11229-021-03414-y. https://doi.org/10.1007/s11229-021-03414-y
  14. Kostić, D., and Khalifa, K. (2025). Does Functional Connectivity Explain? Synthese 206(4) (first online 2025). DOI: 10.1007/s11229-025-05296-w. https://doi.org/10.1007/s11229-025-05296-w
  15. Albantakis, L., Barbosa, L., Findlay, G., Grasso, M., Haun, A. M., Marshall, W., Mayner, W. G. P., Zaeemzadeh, A., Boly, M., Juel, B. E., Sasai, S., Fujii, K., David, I., Hendren, J., Lang, J. P., and Tononi, G. (2023). Integrated Information Theory (IIT) 4.0: Formulating the Properties of Phenomenal Existence in Physical Terms. PLOS Computational Biology 19(10):e1011465. DOI: 10.1371/journal.pcbi.1011465. https://journals.plos.org/ploscompbiol/article?id=10.1371/journal.pcbi.1011465
  16. Grund, M., Forschack, N., Nierhaus, T., and Villringer, A. (2021). Neural Correlates of Conscious Tactile Perception: An Analysis of BOLD Activation Patterns and Graph Metrics. NeuroImage 224:117384. DOI: 10.1016/j.neuroimage.2020.117384. https://doi.org/10.1016/j.neuroimage.2020.117384
  17. Polák, M., and Marvan, T. (2018). Neural Correlates of Consciousness Meet the Theory of Identity. Frontiers in Psychology 9:1269. DOI: 10.3389/fpsyg.2018.01269. https://doi.org/10.3389/fpsyg.2018.01269
  18. Lacalli, T. (2021). Consciousness as a Product of Evolution: Contents, Selector Circuits, and Trajectories in Experience Space. Frontiers in Systems Neuroscience 15:697129. DOI: 10.3389/fnsys.2021.697129. https://doi.org/10.3389/fnsys.2021.697129
  19. Céspedes, E. (2016). Explanatory Exclusion and the Context of Explanation. SpringerBriefs in Philosophy, pp. 59–67. DOI: 10.1007/978-3-319-33801-9_5. https://doi.org/10.1007/978-3-319-33801-9_5