{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,20]],"date-time":"2025-10-20T18:44:09Z","timestamp":1760985849313,"version":"build-2065373602"},"reference-count":34,"publisher":"MDPI AG","issue":"11","license":[{"start":{"date-parts":[[2019,11,2]],"date-time":"2019-11-02T00:00:00Z","timestamp":1572652800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Entropy"],"abstract":"<jats:p>Any theory amenable to scientific inquiry must have testable consequences. This minimal criterion is uniquely challenging for the study of consciousness, as we do not know if it is possible to confirm via observation from the outside whether or not a physical system knows what it feels like to have an inside\u2014a challenge referred to as the \u201chard problem\u201d of consciousness. To arrive at a theory of consciousness, the hard problem has motivated development of phenomenological approaches that adopt assumptions of what properties consciousness has based on first-hand experience and, from these, derive the physical processes that give rise to these properties. A leading theory adopting this approach is Integrated Information Theory (IIT), which assumes our subjective experience is a \u201cunified whole\u201d, subsequently yielding a requirement for physical feedback as a necessary condition for consciousness. Here, we develop a mathematical framework to assess the validity of this assumption by testing it in the context of isomorphic physical systems with and without feedback. The isomorphism allows us to isolate changes in    \u03a6    without affecting the size or functionality of the original system. Indeed, the only mathematical difference between a \u201cconscious\u201d system with     \u03a6 &gt; 0     and an isomorphic \u201cphilosophical zombie\u201d with     \u03a6 = 0     is a permutation of the binary labels used to internally represent functional states. This implies    \u03a6    is sensitive to functionally arbitrary aspects of a particular labeling scheme, with no clear justification in terms of phenomenological differences. In light of this, we argue any quantitative theory of consciousness, including IIT, should be invariant under isomorphisms if it is to avoid the existence of isomorphic philosophical zombies and the epistemological problems they pose.<\/jats:p>","DOI":"10.3390\/e21111073","type":"journal-article","created":{"date-parts":[[2019,11,4]],"date-time":"2019-11-04T04:13:08Z","timestamp":1572840788000},"page":"1073","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":8,"title":["Integrated Information Theory and Isomorphic Feed-Forward Philosophical Zombies"],"prefix":"10.3390","volume":"21","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-0099-993X","authenticated-orcid":false,"given":"Jake R.","family":"Hanson","sequence":"first","affiliation":[{"name":"School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, USA"},{"name":"Beyond Center for Fundamental Concepts in Science, Arizona State University, Tempe, AZ 85281, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5779-2772","authenticated-orcid":false,"given":"Sara I.","family":"Walker","sequence":"additional","affiliation":[{"name":"School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, USA"},{"name":"Beyond Center for Fundamental Concepts in Science, Arizona State University, Tempe, AZ 85281, USA"},{"name":"ASU\u2013SFI Center for Biosocial Complex Systems, Arizona State University, Tempe, AZ 85281, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2019,11,2]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"261","DOI":"10.1038\/nrn783","article-title":"Neural correlates of consciousness in humans","volume":"3","author":"Rees","year":"2002","journal-title":"Nat. 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