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In the quantum case, morphophoric measurements generalise the notion of a 2-design POVM, thus in particular that of a SIC-POVM. We show that the theory built on this class of measurements retains the chief features of the QBism approach to the basis of quantum mechanics. In particular, we demonstrate how to extend the primal equation (&amp;apos;Urgleichung&amp;apos;) of QBism, designed for SIC-POVMs, to the morphophoric case of GPTs. In the latter setting, the equation takes a different, albeit more symmetric, form, but all the quantities that appear in it can be interpreted in probabilistic and operational terms, as in the original &amp;apos;Urgleichung&amp;apos;.<\/jats:p>","DOI":"10.22331\/q-2025-01-15-1598","type":"journal-article","created":{"date-parts":[[2025,1,15]],"date-time":"2025-01-15T17:48:03Z","timestamp":1736963283000},"page":"1598","update-policy":"https:\/\/doi.org\/10.22331\/q-crossmark-policy-page","source":"Crossref","is-referenced-by-count":0,"title":["Can QBism exist without Q? Morphophoric measurements in generalised probabilistic theories"],"prefix":"10.22331","volume":"9","author":[{"given":"Anna","family":"Szymusiak","sequence":"first","affiliation":[{"name":"Institute of Mathematics, Jagiellonian University, \u0141ojasiewicza 6, 30-348 Krak\u00f3w, Poland"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Wojciech","family":"S\u0142omczy\u0144ski","sequence":"additional","affiliation":[{"name":"Institute of Mathematics, Jagiellonian University, \u0141ojasiewicza 6, 30-348 Krak\u00f3w, Poland"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"9598","published-online":{"date-parts":[[2025,1,15]]},"reference":[{"key":"0","doi-asserted-by":"publisher","unstructured":"Aliprantis, CD, Tourky, R, Cones and Duality, AMS, Providence, RI, 2007.","DOI":"10.1090\/gsm\/084"},{"key":"1","doi-asserted-by":"publisher","unstructured":"Appleby, DM, Symmetric informationally complete measurements of arbitrary rank, Opt. 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