{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,2]],"date-time":"2026-06-02T15:51:14Z","timestamp":1780415474279,"version":"3.54.1"},"reference-count":17,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2021,2,27]],"date-time":"2021-02-27T00:00:00Z","timestamp":1614384000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100011730","name":"Templeton World Charity Foundation","doi-asserted-by":"publisher","award":["TWCF0306"],"award-info":[{"award-number":["TWCF0306"]}],"id":[{"id":"10.13039\/501100011730","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001779","name":"Monash University","doi-asserted-by":"publisher","award":["Network of Excellence for Consciousness and Complexity in the Conscious Brain"],"award-info":[{"award-number":["Network of Excellence for Consciousness and Complexity in the Conscious Brain"]}],"id":[{"id":"10.13039\/501100001779","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Entropy"],"abstract":"<jats:p>We summarize the original formulation of the free energy principle and highlight some technical issues. We discuss how these issues affect related results involving generalised coordinates and, where appropriate, mention consequences for and reveal, up to now unacknowledged, differences from newer formulations of the free energy principle. In particular, we reveal that various definitions of the \u201cMarkov blanket\u201d proposed in different works are not equivalent. We show that crucial steps in the free energy argument, which involve rewriting the equations of motion of systems with Markov blankets, are not generally correct without additional (previously unstated) assumptions. We prove by counterexamples that the original free energy lemma, when taken at face value, is wrong. We show further that this free energy lemma, when it does hold, implies the equality of variational density and ergodic conditional density. The interpretation in terms of Bayesian inference hinges on this point, and we hence conclude that it is not sufficiently justified. Additionally, we highlight that the variational densities presented in newer formulations of the free energy principle and lemma are parametrised by different variables than in older works, leading to a substantially different interpretation of the theory. Note that we only highlight some specific problems in the discussed publications. These problems do not rule out conclusively that the general ideas behind the free energy principle are worth pursuing.<\/jats:p>","DOI":"10.3390\/e23030293","type":"journal-article","created":{"date-parts":[[2021,2,27]],"date-time":"2021-02-27T20:55:44Z","timestamp":1614459344000},"page":"293","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":40,"title":["A Technical Critique of Some Parts of the Free Energy Principle"],"prefix":"10.3390","volume":"23","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-1670-6855","authenticated-orcid":false,"given":"Martin","family":"Biehl","sequence":"first","affiliation":[{"name":"Araya Inc., Tokyo 107-6024, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1483-5661","authenticated-orcid":false,"given":"Felix A.","family":"Pollock","sequence":"additional","affiliation":[{"name":"School of Physics and Astronomy, Monash University, Clayton, VIC 3800, Australia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0186-2687","authenticated-orcid":false,"given":"Ryota","family":"Kanai","sequence":"additional","affiliation":[{"name":"Araya Inc., Tokyo 107-6024, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2021,2,27]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"2013.0475","DOI":"10.1098\/rsif.2013.0475","article-title":"Life as we know it","volume":"10","author":"Friston","year":"2013","journal-title":"J. R. Soc. Interface"},{"key":"ref_2","unstructured":"Friston, K. (2019). A free energy principle for a particular physics. arXiv."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"2019.0159","DOI":"10.1098\/rsta.2019.0159","article-title":"Markov blankets, information geometry and stochastic thermodynamics","volume":"378","author":"Parr","year":"2019","journal-title":"Philos. Trans. R. Soc. A"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"427","DOI":"10.1109\/JPROC.2014.2306251","article-title":"Cognitive Dynamics: From Attractors to Active Inference","volume":"102","author":"Friston","year":"2014","journal-title":"Proc. IEEE"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"187","DOI":"10.1080\/17588928.2015.1020053","article-title":"Active inference and epistemic value","volume":"6","author":"Friston","year":"2015","journal-title":"Cogn. 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Ergodic Theory, Springer.","DOI":"10.1007\/978-1-4615-6927-5"}],"container-title":["Entropy"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1099-4300\/23\/3\/293\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T05:30:09Z","timestamp":1760160609000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1099-4300\/23\/3\/293"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,2,27]]},"references-count":17,"journal-issue":{"issue":"3","published-online":{"date-parts":[[2021,3]]}},"alternative-id":["e23030293"],"URL":"https:\/\/doi.org\/10.3390\/e23030293","relation":{},"ISSN":["1099-4300"],"issn-type":[{"value":"1099-4300","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,2,27]]}}}